Sisimai: Mail Analyzing Interface

Bounce Reason List

Sisimai can detect 34 types of bounce reasons by decoding bounce emails. You can obtain the detected bounce reason from the reason() accessor of the Sisimai::Fact object. the value of "reason" is always lowercase, such as "userunknown" or "expired".

By Address

This is a list of bounce reasons that are caused by problems with the sender's or recipient's email address or mailbox.

Read

By Content

This is a list of bounce reasons that are caused by problems with the content of the sent email, including some headers and the body.

Read

By Server

This is a list of bounce reasons that are caused by problems with the state of the sender's or recipient's server.

Read

Others

This is a list of other bounce reasons, including those that Sisimai could not identify the cause.

Read

Table of Bounce Reasons

Sisimai can detect 34 types of bounce reasons and sets the bounce reason in the "reason" field of the decoded data. The value of "reason" is always lowercase, such as "userunknown" or "expired".

To get a list of all detectable bounce reasons, refer to the return value of the reason() method of the Sisimai class.

Reason Name Hard Bounce Description
Host Unknown Yes Destination host name does not exist
User Unknown Yes Recipient's address does not exist
Filtered No Rejected after DATA command
Has Moved Yes Destination mail addrees has moved
Rejected No Rejected due to envelope from address
Mailbox Full No Recipient's mailbox is full
Suspend No Recipient's account is suspended
Content Error No Email body or header is invalid format
Exceed Limit No Message size exceeded the limit(5.2.3)
Feedback No Bounced for a complaint of the message(FBL)
Mesg Too Big No Message size is too big(5.3.4)
Not Compliant RFC No Email rejected due to non-compliance with RFC
Policy Violation No Violation of security policies
Security Error No Authentication error and so on
Virus Detected No Virus, worm or malware detected
Spam Detected No Detected a message as spam
Auth Failure No Email rejected due to SPF, DKIM, DMARC failure
Bad Reputation No Email rejected due to an IP address reputation
Blocked No Blocked due to client IP address or hostname
Expired No Delivery time expired
Mailer Error No Mailer program error on remote host
Network Error No Network error: DNS or routing
No Relaying No Relay access denied
Not Accept No Destination does not accept any message
Require PTR No Email rejected due to missing PTR record or having invalid PTR record
Speeding No Rejected due to exceeding a rate limit or sending too fast
System Error No Some error on the destination host
System Full No Disk full on the destination host
Too Many Conn No Connection rate limit exceeded
Delivered No Successfully delivered
Syntax Error No syntax error in SMTP
Vacation No Auto replied message (recipient is away)
On Hold No Deciding the bounce reason is on hold
Undefined No Could not decide an error reason

Rejected By Address

This document provides a list of bounce reasons that are caused by problems with the sender's or recipient's email address, or the state of the recipient's mailbox.

Host Unknown (Hard bounce)

This error is returned when the domain part (the string to the right of the "@" symbol) of the destination email address is an unknown host or a non-existent domain name. In many cases, this is caused by a typo in the domain name, an invalid DNS record, or a domain that has been discontinued. In Sisimai's internal processing, this reason is also determined when the value of the Status: field in the bounce email is "5.1.2". 

Your message to the following recipients cannot be delivered:

<kijitora@example.cat>:
<<< No such domain.
  • No such domain.
  • all host address lookups failed permanently
  • all relevant MX records point to non-existent hosts
  • Unrouteable address
  • 554 5.4.4 SMTPSEND.DNS.NonExistentDomain
  • Illegal host/domain name found
  • Sorry, I couldn't find any host by that name. (#4.1.2)
  • Host or domain name not found
  • The mail could not be delivered to the recipient because the domain is not reachable

User Unknown (Hard bounce)

This error is returned when the local part (the string to the left of the "@" symbol) of the destination email address is a non-existent user. This is often the case for users who have changed their email address (for mobile phones) or have canceled their provider subscription (for PCs), or for users who have left a company or organization. 

<kijitora@example.co.jp>: host mx01.example.co.jp[192.0.2.8] said:
  550 5.1.1 Address rejected kijitora@example.co.jp (in reply to RCPT TO command)

In Sisimai's internal bounce email processing, this reason is determined when the value of the "Status:" field is "5.1.1", when the connection is rejected with RCPT TO: in the SMTP session, or when the "Diagnostic-Code:" header indicates that the recipient is unknown.

  • not listed in Domino Directory / Public Name & Address Book
  • 550 5.1.1 RESOLVER.ADR.RecipNotFound
  • 550 5.1.1 RESOLVER.ADR.ExRecipNotFound
  • Invalid final delivery userid
  • Sorry, no mailbox here by that name. (#5.1.1)
  • <neko@example.jp>: 192.0.2.153 does not like recipient. Remote host said: 550 5.2.1 ...
  • Requested action not taken: mailbox unavailable

Filtered

This error is returned when the user has configured their email settings to reject emails, or when the mailbox exists but is not receiving emails. For deliveries to mobile phones in Japan (3 major carriers), this reason is determined if the domain is blocked (excluded from domain-specified reception) or if the email is rejected by a URL filter.

This error reason is nearly identical to UserUnknown. 

... while talking to mfsmax.ntt.example.ne.jp.:
>>> DATA
<<< 550 Unknown user kijitora@ntt.example.ne.jp
554 5.0.0 Service unavailable

In Sisimai's internal bounce email processing, this reason is also determined when the value of the "Status:" field is "5.2.0" or "5.2.1", or when the email is rejected based on the content after the DATA command in the SMTP session.

  • Cannot route mail to user
  • 550 5.7.1 RESOLVER.RST.AuthRequired
  • 550 5.2.1 <kijitora@example.jp>... User Unknown
  • 550 Unknown user kijitora@example.net (in reply to end of DATA command)
  • 554 delivery error: dd This user doesn't have a yahoo.com account (this-local-part-does-not-exist@yahoo.com) [0] - mta1061.mail.ne1.yahoo.com
  • 550 5.1.1 RCP-P2 http://postmaster.facebook.com/response_codes?ip=192.0.2.135#rcp Refused due to recipient preferences

Has Moved (Hard bounce)

This error is returned when the recipient's mailbox has been moved to another address (and automatic forwarding is not set up). In Sisimai's internal bounce email processing, this reason is determined when the value of the "Status:" field is "5.1.6". 

<kijitora@example.go.jp>: host mx1.example.go.jp[192.0.2.127] said: 550 5.1.6 recipient
no longer on server: kijitora@example.go.jp (in reply to RCPT TO command)
  • <kijitora@example.go.jp>: host mx1.example.go.jp[192.0.2.127] said: 550 5.1.6 recipient no longer on server: kijitora@example.go.jp (in reply to RCPT TO command)
  • 551 not our user
  • 551 not our customer
  • The e-mail address neko@example.jp has been replaced by nyaan@example.jp

Rejected

This error is returned when the email is rejected by the sender's address (Envelope From). In Sisimai's internal bounce email processing, this reason is determined when the value of the "Status:" field is "5.1.8", or when the email is rejected based on the content of the MAIL FROM: command in the SMTP session. 

<kijitora@example.org>:
Connected to 192.0.2.225 but sender was rejected.
Remote host said: 550 5.7.1 <root@nijo.example.jp>... Access denied
  • 550 5.7.1 RESOLVER.RST.NotAuthorized
  • 553 5.1.8 <neko@neko.example.jp>... Domain of sender address root@neko.example.jp does not exist (in reply to MAIL FROM command)
  • Connected to 192.0.2.225 but sender was rejected. Remote host said: 550 5.7.1 <neko@nijo.example.jp>... Access denied
  • 553 5.1.8 <neko@nyaan.example.jp>... Domain of sender address neko@nyaan.example.jp does not exist
  • SMTP error from remote mail server after MAIL FROM:<neko@nyaan.example.jp> SIZE=1420: host mx.libsisimai.org [192.0.2.135]: 550 5.1.8 <neko@nyaan.example.jp>... Error

Mailbox Full

This error is returned when the recipient's mailbox is full (exceeding the maximum storage capacity specified by the mail server). This applies to both mobile phones and PCs, and occurs when the user has not received emails and left them on the server, or has received emails but has not deleted them from the server. 

Action: failed
Status: 5.2.2
Diagnostic-Code: smtp;550 5.2.2 <kijitora@example.jp>... Mailbox Full

In Sisimai's internal bounce email processing, this reason is determined when the value of the "Status:" field is "4.2.2" or "5.2.2". This error is returned when the email is rejected by the sender's address (Envelope From).

  • mailbox is full
  • User mailbox exceeds allowed size
  • 552 Error: disk quota exceeded
  • Could not be delivered to: <kijitora@**.**.ne.jp> As their mailbox is full.
  • The number of messages in recipient's mailbox exceeded the local limit.
  • The user(s) account is temporarily over quota
  • The recipient's mailbox is full and can't accept messages now.
  • #550 5.2.2 STOREDRV.Deliver: mailbox full.
  • The e-mail message could not be delivered because the user's mailfolder is full.
  • This person's account is exceeding their quota.
  • host gmail-smtp-in.l.google.com[108.177.125.26] said: The recipient's inbox is out of storage space and inactive. Please direct the recipient to https://support.google.com/mail/?p=OverQuotaPerm c2-202229zmZBNM3agi23.222 - gsmtp (in reply to RCPT TO command)

Suspend

This error is detected when the user has unpaid charges for au by KDDI. This error may also occur if the account is temporarily suspended for some reason, even for emails to Gmail or Yahoo!. 

SMTP error from remote mail server after end of data: host mx2.mail.yahoo.com [192.0.2.222]:
554 delivery error: dd Sorry your message to **@yahoo.com.ar cannot be delivered.
This account has been disabled or discontinued [#102]. - mta497.mail.mud.yahoo.com"
  • Mailaddress is administratively disabled
  • The user(s) account is disabled.
  • The user(s) account is temporarily limited.
  • dd Sorry your message to ****@yahoo.com.ar cannot be delivered. This account has been disabled or discontinued [#102].
  • 525 5.7.13 Disabled recipient address
  • 550 [SUSPEND] Mailbox currently suspended - Please contact correspondent directly

Rejected By Content

The following is a list of bounce reasons that were caused by the content of the email body or some of the headers. Most of them are caused by inspection by the MTA's program or spam filter.

Content Error

This error category includes cases where the format of the sent email cannot be converted or understood by the destination mail server. In the internal process of bounce email processing performed by Sisimai, this reason is determined when the value of the "Status:" field is "5.6.x".

Examples of cases that fall into this category:

  • The header contains 8-bit data.
  • There are too many "Received:" headers.
  • The MIME header is invalid.
... while talking to g5.example.net.:
>>> DATA
<<< 550 5.6.9 improper use of 8-bit data in message header
554 5.0.0 Service unavailable
  • Too many "Received" headers - suspected mail loop
  • 550 5.6.9 improper use of 8-bit data in message header
  • 500 5.6.1 Message content rejected

Exceed Limit

This error is returned when the amount of email sent to the recipient exceeds the limit set on the server. Specifically, this occurs when the size of the sent email is larger than the default value, and is almost the same as MesgTooBig described later. In Sendmail's deliver.c, it is implemented as follows to determine whether this reason or MesgTooBig applies depending on the recipient. 

1586: if (bitnset(M_LOCALMAILER, to->q_mailer->m_flags))
1587:     to->q_status = "5.2.3";
1588: else
1589:     to->q_status = "5.3.4";
                
... while talking to mx.example.org.:
>>> MAIL From:<kijitora@example.co.jp> SIZE=16600348
<<< 552 5.2.3 Message size exceeds fixed maximum message size (10485760)
554 5.0.0 Service unavailable

In the internal process of bounce email processing performed by Sisimai, this reason is determined when the value of the "Status:" field is "4.2.3" or "5.2.3".

  • The message exeeded the maximum size the user accepts
  • 552 5.2.3 Message size exceeds fixed maximum message size (10485760)
  • maildir delivery failed: Sorry, the user's maildir has overdrawn his diskspace quota, please try again later.
  • 552-5.2.3 Your message exceeded Google's message size limits. Please visit http://mail.google.com/support/bin/answer.py?answer=8770 to review our size guidelines.
  • 552 5.2.3 Message exceeds local size limit.
  • 550 5.2.3 RESOLVER.RST.SendSizeLimit.Org; message too large for this organization

Feedback

When Sisimai decodes an ARF-formatted email sent when a recipient complains to their provider, it determines this reason. The decoded result of the email that becomes this reason is expressed in JSON format as follows. 

[
    {
        "token": "491f2fd0f90ee3017f2ab2eb67a1239b78a84321",
        "deliverystatus": "",
        "destination": "yahoo.com",
        "timezoneoffset": "-0800",
        "smtpcommand": "",
        "listid": "",
        "replycode": "",
        "subject": "Nyaaaaaaaan",
        "diagnostictype": "SMTP",
        "diagnosticcode": "This is an email abuse report for an email message received from mx8.example.com  on Thu, 29 Apr 2013 23:45:00 PST",
        "senderdomain": "example.com",
        "feedbacktype": "abuse",
        "alias": "",
        "reason": "feedback",
        "addresser": "shironeko@example.com",
        "lhost": "smtp-gw83.example.com",
        "smtpagent": "Yahoo!-Mail-Feedback/1.0",
        "rhost": "uid",
        "messageid": "000000000000000000000000.smtp@example.com",
        "action": "failed",
        "recipient": "this-local-part-does-not-exist-on-yahoo@yahoo.com",
        "timestamp": 1367307950
    }
]
  • If you would like to cancel or change the configuration for your FBL please use the tool located at: http://postmaster.example.net/waters/fbl_change_form.html
  • This is an email abuse report for an email message received from IP 192.0.2.45 on Wed, 12 Nov 2014 12:40:48 +0000. The message below did not meet the sending domain's dmarc policy. For more information about this format please see http://tools.ietf.org/html/rfc6591 .
  • This is an opt-out report for an email message received from IP 192.0.2.89 on Thu, 9 Apr 2006 23:34:45 JST. For more information about this format please see http://www.example.org/arf/.

Message Too Big (mesgtoobig)

This error is returned when the size of the sent email exceeds the allowable size of the recipient's mail server. In many cases, this error occurs when the attached file is too large or when the total size exceeds the limit due to multiple attached files. 

Action: failure
Status: 553 Exceeded maximum inbound message size

In the internal process of bounce email processing performed by Sisimai, this reason is determined when the value of the "Status:" field is "5.3.4".

  • 550 5.2.3 RESOLVER.RST.RecipSizeLimit
  • sorry, that message size exceeds my databytes limit (#5.3.4)
  • 552 sorry, that message size exceeds my databytes limit (#5.3.4)
  • 553 Exceeded maximum inbound message size
  • Mail size limit exceeded.
  • 552 5.3.4 Message too large
  • message size 18876259 exceeds size limit 10485760 of server neko.example.jp[192.0.2.2]
  • 534 SIZE=Message too big. (in reply to MAIL FROM command)
  • 554 5.7.1 Message Rejected Class=size limit=15728640 Subclass=reject size=18571048 (in reply to end of DATA command)
  • Remote host said: 552 Message size exceeds fixed maximum message size: 1048576 bytes
  • 552 Message size exceeds maximum value

Not Compliant RFC

This error is returned when there is an email header that does not comply with or violates the RFC5322 specification. For example, if the From: header, which should be a single mandatory header, is missing or there are multiple instances of it, or if there are multiple "Subject:" headers, the email will be considered an RFC violation. This bounce reason was implemented in Sisimai 5.0.0 as a separate category from Security Error. 

Action: failed
Status: 5.7.1
Remote-MTA: dns; gmail-smtp-in.l.google.com
Diagnostic-Code: smtp; 550-5.7.1 host aspmx.l.google.com[142.251.170.26] said: This message
    is not RFC 5322 compliant. There are multiple Subject headers. To reduce the amount of
    spam sent to Gmail, this message has been blocked.
    Please visit https://support.google.com/mail/?p=RfcMessageNonCompliant and review RFC 5322
    specifications for more information. c2-aguiqyuiyuqir5678167856aeu8.22 - 
    gsmtp (in reply to end of DATA command)"
  • Messages with multiple 550 5.7.1 addresses in From: header are not accepted. v14si1155795plk.134 - gsmtp
  • host aspmx.l.google.com[142.251.170.26] said: This message is not RFC 5322 compliant. There are multiple Subject headers. To reduce the amount of spam sent to Gmail, this message has been blocked. Please visit https://support.google.com/mail/?p=RfcMessageNonCompliant and review RFC 5322 specifications for more information. c2-aguiqyuiyuqir5678167856aeu8.22 - gsmtp (in reply to end of DATA command)"

Policy Violation

This error is returned when the recipient's mail server rejects the email due to a policy violation. The specific types of policy violations vary depending on the individual mail server's policy, so it is often difficult to determine the exact cause of the bounce. 

Action: failed
Status: 5.7.1
Remote-MTA: dns; gmail-smtp-in.l.google.com
Diagnostic-Code: smtp; 550-5.7.1 [2401:2500:102:3032:192.0.2.222      13]
    Messages with multiple 550 5.7.1 addresses in From: header are not
    accepted. v14si1155795plk.134 - gsmtp

This bounce reason was implemented in Sisimai 4.22.0 as a separate category from Security Error. It is not implemented in bounceHammer.

  • 554 email rejected due to security policies
  • Technical details of permanent failure: You have exceeded the the allowable number of posts without solving a captcha.
  • SMTP error from remote mail server after end of data: host mx.example.jp [192.0.2.20]: 554 5.7.0 Header error
  • SMTP; 554 5.7.9 Header error

Security Error

This error is returned when the recipient's mail server rejects the email for security reasons. The specific types of security errors vary depending on the individual mail server's policy, but may include sender address spoofing and authentication errors. 

552-5.7.0 This message was blocked because its content presents a potential
552-5.7.0 security issue. Please visit
552-5.7.0  https://support.google.com/mail/answer/6590 to review our message
552 5.7.0 content and attachment content guidelines. p4si4011367igr.94 - gsmtp

In the internal process of bounce email processing performed by Sisimai, this reason is determined when the value of the "Status:" field is "5.7.x".

In Sisimai 4.22.0, Policy Violation and Virus Detected were implemented as separate categories from this bounce reason.

In Sisimai 5.0.0, Auth Failure, Not Compliant RFC, and Speeding were further implemented as separate categories from this bounce reason.

  • Could not retrieve credentials
  • 552-5.7.0 This message was blocked because its content presents a potential security issue.
  • SMTP Server <mta.neko.exampe.jp> rejected recipient <nyaan@neko.example.jp> (Error following RCPT command). It responded as follows: [550 Previous (cached) callout verification failure]
  • 553 From <>, message blocked, you are not authorized to send mail, authentication is required.

Virus Detected

This error is returned when the recipient's mail server detects a harmful file or program, such as a virus, worm, or malware, in the email. 

Status: 5.7.0
Remote-MTA: DNS; gmail-smtp-in.l.google.com
Diagnostic-Code: SMTP; 552-5.7.0 Our system detected an illegal attachment on your message. Please

This bounce reason was implemented in Sisimai 4.22.0 as a separate category from Security Error. It is not implemented in bounceHammer.

  • Requested action not taken: virus detected
  • 552-5.7.0 Our system detected an illegal attachment on your message. Please visit http://mail.google.com/support/bin/answer.py?answer=6590 to review our attachment guidelines.
  • Your message was infected with a virus. You should download a virus scanner and check your computer for viruses.

Spam Detected

If the sent email is detected as spam, or if the sending host is recognized as a spam sending host by DNSBL, Sisimai determines the bounce reason as SpamDetected. This bounce reason was implemented in Sisimai 4.1.25 and is not implemented in bounceHammer. 

Action: failed
Status: 5.7.1
Diagnostic-Code: smtp; 550 5.7.1 Message content rejected, UBE, id=00000-00-000
Last-Attempt-Date: Thu, 9 Apr 2008 23:34:45 +0900 (JST)

  • Our system has detected that this message is likely unsolicited mail.
  • 550 5.7.1 message content rejected
  • 550 Spam refused.
  • 554 imta14.emeryville.ca.mail.comcast.net comcast 192.0.2.4 Comcast block for spam. Please see http://postmaster.comcast.net/smtp-error-codes.php#BL000000
  • User profile spam level exceeded
  • 550-Blacklisted URL in message. (example.com) in [black]. See http://lookup.uribl.com.
  • 550-5.7.1 [192.0.2.6] Our system has detected that this message is likely unsolicited mail. To reduce the amount of spam sent to Gmail, this message has been blocked. Please visit http://support.google.com/mail/bin/answer.py?hl=en&answer=188131 for more information.
  • 550 5.7.1 Your email breaches local URIBL policy. (in reply to end of DATA command)
  • 554 5.7.1 Message cannot be accepted, spam rejection (in reply to end of DATA command)
  • 550 Error: SPAM-ID: e00000000-000000 Your email had spam-like header contents. Please contact your email service provider. (in reply to end of DATA command)
  • 550 ****(0000): Your email was detected as spam. (RCPTs: neko@example.org) (in reply to end of DATA command)
  • 550 Denied due to spam list (in reply to RCPT TO command)
  • 554 5.7.1 Mail (22222-22222) appears to be unsolicited - Score (222) over MessageScoringUpperLimit (22) - send error reports to postmaster@example.org
  • 554 5.7.1 Your message failed several antispam checks (SCORING) and it was rejected or collected on example.net spambox. Please be sure your mailserver is configured correctly (spf , HELO, PTR) or try using an alternative email or smtp.
  • 550 Probable Spam (in reply to end of DATA command)
  • 550 5.7.1 Message content rejected, UBE, id=00000-00-000

Rejected By Server

The following is a list of bounce reasons that are caused by the state of the sending or receiving MTA. Many of these are caused by the sender's IP address, hostname, the number of connections to the destination server, or the state of other backends.

Auth Failure

This error is returned when domain authentication using SPF, DKIM, DMARC, or ARC fails. It often occurs when domain authentication fails in multiple factors, such as when it fails in both SPF and DKIM. This bounce reason was implemented in Sisimai 5.0.0. 

Action: failed
Status: 5.7.26
Remote-MTA: dns; gmail-smtp-in.l.google.com
Diagnostic-Code: smtp;
    550-5.7.26 This mail has been blocked because the sender is unauthenticated.
    550-5.7.26 Gmail requires all senders to authenticate with either SPF or DKIM.
    550-5.7.26 Authentication results:
    550-5.7.26  DKIM = did not pass
    550-5.7.26  SPF [relay3.example.com] with ip: [192.0.2.22] = did not pass
    550-5.7.26 For instructions on setting up authentication, go to
    550 5.7.26 https://support.google.com/mail/answer/81126#authentication
    c2-202200202020202020222222cat.127 - gsmtp
  • Diagnostic information for administrators: kijitora@example.com neko-smtp-02-22.prod.cats.secureserver.net Remote Server returned '550 5.1.0 192.0.2.222 is not allowed to send from per it's SPF Record. Please inspect your SPF settings, and try again. IB508 '
  • host gmail-smtp-in.l.google.com[64.233.189.27] said: Unauthenticated email from libsisimai.org is not accepted due to domain's DMARC policy. Please contact the administrator of libsisimai.org domain if this was a legitimate mail. Please visit https://support.google.com/mail/answer/2451690 to learn about the DMARC initiative. z2si1584129pfn.61 - gsmtp (in reply to end of DATA command)
  • host mx01.mail.icloud.com[17.57.152.9] said: 554 5.7.1 Your message was rejected due to libsisimai.org's DMARC policy. See https://support.apple.com/en-us/HT204137 for info (in reply to end of DATA command)
  • host mxs.mail.ru[94.100.180.31] said: 550 5.7.1 This message was not accepted due to domain (libsisimai.org) owner DMARC policy (RFC 7489) https://help.mail.ru/mail-help/postmaster/dmarc (in reply to end of DATA command)
  • host gmail-smtp-in.l.google.com[64.233.187.27] said: This mail has been blocked because the sender is unauthenticated. Gmail requires all senders to authenticate with either SPF or DKIM. Authentication results: DKIM = did not pass SPF [relay3.example.com] with ip: [192.0.2.22] = did not pass For instructions on setting up authentication, go to https://support.google.com/mail/answer/81126#authentication c2-202200202020202020222222cat.127 - gsmtp (in reply to end of DATA command)
  • host gmail-smtp-in.l.google.com[64.233.188.26] said: The MAIL FROM domain [mail4.example.com] has an SPF record with a hard fail policy (-all) but it fails to pass SPF checks with the ip: [192.0.2.24]. To best protect our users from spam and phishing, the message has been blocked. For instructions on setting up authentication, go to https://support.google.com/mail/answer/81126#authentication 2-222222630d46222222b002b2d2neko2cat2222222cat.22 - gsmtp (in reply to end of DATA command)",

Bad Reputation

This error is returned when the sender's IP address or domain has a low reputation score on the receiving host, and the email is rejected for that reason. You may see this error when sending to large email service providers such as Gmail or Outlook. This bounce reason was implemented in Sisimai 5.0.0. 

Action: failed
Status: 5.7.1
Remote-MTA: dns; gmail-smtp-in.l.google.com
Diagnostic-Code: smtp; 550-5.7.1 [192.0.2.22      18] Our system has
    detected that this message is 550-5.7.1 likely suspicious due to the very
    low reputation of the sending IP 550-5.7.1 address. To best protect our
    users from spam, the message has been 550-5.7.1 blocked. Please visit 550
    5.7.1  https://support.google.com/mail/answer/188131 for more information.
    p22nn000202cat.22 - gsmtp
  • [192.0.2.22 18] Our system has detected that this message is likely suspicious due to the very low reputation of the sending IP address. To best protect our users from spam, the message has been blocked. Please visit https://support.google.com/mail/answer/188131 for more information. p22nn000202cat.22 - gsmtp
  • host hotmail-com.olc.protection.outlook.com[104.47.66.33] said: 451 4.7.650 The mail server [192.0.2.25] has been temporarily rate limited due to IP reputation. For e-mail delivery information, see https://postmaster.live.com (S775) (in reply to MAIL FROM command))

Blocked

This bounce reason is determined by Sisimai when the connection to the destination host is rejected due to the IP address, hostname, or EHLO, EHLO command value of the sending mail server. This bounce reason was implemented in Sisimai 4.0.0 and is not implemented in bounceHammer. 

<kijitora@example.net>: 
Connected to 192.0.2.112 but my name was rejected. 
Remote host said: 501 5.0.0 Invalid domain name
  • 550 5.7.1 can't determine Purported Responsible Address
  • SMTP error from remote mail server after MAIL FROM:<shironeko@example.jp> SIZE=1543: host mx.example.jp [192.0.2.20]: 550 5.7.0 <shironeko@example.jp>... Please use the smtp server of your ISP.
  • host mxs.mail.ru[194.67.23.20] said: 550 Access from ip address 192.0.2.4 blocked. Visit http://win.mail.ru/cgi-bin/support_bl?ip=192.0.2.4 (in reply to RCPT TO command)
  • Connected to 192.0.2.112 but my name was rejected. Remote host said: 501 5.0.0 Invalid domain name
  • 450 4.7.1 Access denied. IP name lookup failed [192.0.2.222]
  • 5.1.0 - Unknown address error 550-'5.7.1 <000001321defbd2a-788e31c8-2be1-422f-a8d4-cf7765cc9ed7-000000@email-bounces.amazonses.com>... Access denied' (delivery attempts: 0)
  • The error that the other server returned was: 554 554 5.7.1 Service unavailable; Client host [192.0.2.49] blocked using cbl.abuseat.org (state 13).

Expired

This error category includes emails that are bounced back due to delivery timeouts, such as when the email cannot connect to the destination host. If the reason for the delivery failure is DNS resolution, the bounce reason may be NetworkError. 

kijitora@example.org
(ultimately generated from nekochan@example.org)
all hosts have been failing for a long time and were last
tried after this message arrived
  • 550 4.4.7 QUEUE.Expired
  • Delivery failed 22 attempts
  • Envelope expired
  • retry timeout exceeded
  • Your message was not delivered within 0 days and 1 hours.
  • Host not reachable
  • 4.4.7 (unable to deliver this message after 1 day)
  • <neko@nyan.example.org>: connect to nyaan.example.org[192.0.2.1]:25: Connection timed out
  • Deferred: 421 Message could not be delivered for 8 hours Message will be deleted from queue
  • 421 example.com (smtp)... Deferred: Connection timed out during user open with example.com
  • Routing: Could not find a gateway for kijitora@example.co.jp
  • Delevery to the following recipients was aborted after 5.0 hour(s):
  • The following message, addressed to 'neko@nyaan.example.jp', failed because it has not been collected after 30 days
  • 5.4.7 - Delivery expired (message too old) 'timeout' (delivery attempts: 0)
  • 554 4.4.7 Message expired: unable to deliver in 840 minutes. <421 4.4.2 Connection timed out> Status: 4.4.7
  • Unable to deliver message to the following recipients, due to being unable to connect successfully to the destination mail server.
  • kijitora:00000:<kijitora@example.org> : Connection timed out in connect
  • kijitora@7jo.example.jp Error, ERROR_CODE :421, ERROR_CODE :, Host not reachable.

Mailer Error

This error is returned when the program that is supposed to be launched upon receiving an email fails to terminate normally. This is often caused by a bug in the program or insufficient exception handling when connecting to a required backend service (such as a database). 

X-Actual-Recipient: X-Unix; |/home/kijitora/mail/catch.php
Diagnostic-Code: X-Unix; 255
  • 554 5.3.0 unknown mailer error 255
  • <r@p351355.pool.example.ne.jp> (expanded from <kijitora@example.org>): user unknown. Command output: procmail: Couldn't create "/var/spool/mail/neko" id: r.example.org: No such user
  • |IFS=' ' && exec /usr/local/bin/procmail -f- || exit 75 #kijitora@mailx-53.neko.example.edu
  • temporary failure. Command output: avpcheck: unable to connect to avp daemon: Connection refused
  • Command died with status 17: "/usr/sbin/amavis". Command output: Can't use an undefined value as a symbol reference at /usr/sbin/amavis line 1178.

Network Error

This bounce reason is determined by Sisimai when an SMTP connection cannot be established due to DNS resolution failure or other network-related errors that prevent the email from being sent. This bounce reason was implemented in Sisimai 4.1.12 and is not implemented in bounceHammer. 

A message is delayed for more than 10 minutes for the following
list of recipients:

kijitora@neko.example.jp: Network error on destination MXs
  • DNS lookup failed.
  • 554 5.4.4 SMTPSEND.DNS.MxLoopback
  • Message has exceeded maximum hop count
  • Temporary failure in MX lookup
  • Address family mismatch on destination MXs
  • unrouteable mail domain "non-local.example" (:fail:)
  • Name service error for name=example.org type=MX: Malformed or unexpected name server reply
  • Name service error for domain digicool.com: Host not found, try again
  • Sorry, I wasn't able to establish an SMTP connection. (#4.4.1)
  • 554 5.4.6 Too many hops 26 (25 max): from <shironeko@example.jp> via localhost, to <kijitora@example.com>
  • Unable to deliver message to the following recipients, because the message was forwarded more than the maximum allowed times. This could indicate a mail loop.

No Relaying

This bounce reason is determined by Sisimai when an email is bounced due to SMTP relay rejection. This bounce reason is not implemented in bounceHammer. 

... while talking to mailin-01.mx.example.com.:
>>> RCPT To:<kijitora@example.org>
<<< 554 5.7.1 <kijitora@example.org>: Relay access denied
554 5.0.0 Service unavailable
  • Due to the following SMTP relay error
  • host neko.example.com[192.0.2.22] said: 550 5.7.1 Unable to relay for nyaan@neko.example.com (in reply to RCPT TO command)
  • 192.0.2.1 does not like recipient. Remote host said: 554 5.7.1 <neko@example.com>: Relay access denied
  • 554 5.7.1 <kijitora@example.org>: Relay access denied
  • 550 Insecure Mail Relay

Not Accept

This error is returned when the recipient's mail server cannot receive the email. This error can occur if the destination mail server is overloaded or under maintenance. In the internal process of the bounce email processing performed by Sisimai, this reason is determined for emails with a "5.3.2" value in the "Status:" field or a "556" value in the SMTP reply code. Additionally, this bounce reason also includes cases where the sender domain is a NullMX.

  • an MX or SRV record indicated no SMTP service
  • no host found for existing SMTP connection
  • Destination seem to reject all mails
  • No mx record found for domain=libsisimai.org
  • host/domain does not accept mail
  • DNS Error: 24275403 DNS type 'mx' lookup of libsisimai.org responded with code NOERROR The domain libsisimai.org doesn't receive email according to the administrator: returned Null MX https://www.rfc-editor.org/info/rfc7505
  • Name service error for name=libsisimai.org type=MX: Malformed or unexpected name server reply

Require PTR

This error is returned when the PTR record (reverse lookup record) is not set or is incorrect for the source IP address that made the SMTP connection. Some email service providers strictly verify reverse lookups, so at least some reverse lookup configuration is required. 

Action: failed
Status: 5.7.25
Remote-MTA: dns; gmail-smtp-in.l.google.com
Diagnostic-Code: smtp; 550-5.7.25 [192.0.2.202] The IP address sending this
    message does not have a 550-5.7.25 PTR record setup, or the corresponding
    forward DNS entry does not 550-5.7.25 point to the sending IP. As a policy,
    Gmail does not accept messages 550-5.7.25 from IPs with missing PTR
    records. For more information, go to 550 5.7.25
    https://support.google.com/mail/answer/81126#ip-practices
    neko-1785a7g6767a6agg.2 - gsmtp

This bounce reason was implemented in Sisimai 5.0.0 as a separate category from Blocked.

  • host relay.example.net [192.0.2.222] SMTP error from remote mail server after initial connection: 571 No PTR Record found. Reverse DNS required: 203.0.113.22"
  • host mx1.comcast.net [192.0.2.222] SMTP error from remote mail server after initial connection: 554 mta1.comcast.net comcast 203.0.113.2 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to: http://postmaster.comcast.net/smtp-error-codes.php#554
  • host mx2.example.net [192.0.2.222] SMTP error from remote mail server after MAIL FROM: SIZE=1024: 554 5.7.1 Reverse DNS failed.
  • host mx01.mail.com[74.208.5.22] refused to talk to me: mail.com (mxgmxus002) Nemesis ESMTP Service not available No SMTP service Bad DNS PTR resource record. For explanation visit http://postmaster.gmx.com/en/error-messages?ip=192.0.2.22&c=rdns
  • 450 4.7.1 Access denied. IP name lookup failed [192.0.2.222] 450 4.7.1 Access denied. IP name lookup failed [192.0.2.222]
  • host gmail-smtp-in.l.google.com[142.251.170.27] said: [192.0.2.202] The IP address sending this message does not have a PTR record setup, or the corresponding forward DNS entry does not point to the sending IP. As a policy, Gmail does not accept messages from IPs with missing PTR records. For more information, go to https://support.google.com/mail/answer/81126#ip-practices

Speeding

This error occurs when the recipient host has a per-unit-time traffic limit and that limit has been exceeded. This means that the sender's email sending speed is too fast. This bounce reason was implemented in Sisimai 5.0.0 as a separate category from Security Error or Too Many Conn. 

Status: 5.2.1
Remote-MTA: dns; alt1.gmail-smtp-in.l.google.com
Diagnostic-Code: smtp; 550-5.2.1 The user you are trying to contact is
    receiving mail at a rate that 550-5.2.1 prevents additional messages from
    being delivered. For more 550-5.2.1 information, please visit 550 5.2.1
    https://support.google.com/mail/?p=ReceivingRatePerm p131si8414989oif.118 -
    gsmtp
  • host alt1.gmail-smtp-in.l.google.com[74.125.127.27] said: The user you are trying to contact is receiving mail at a rate that prevents additional messages from being delivered. For more information, please visit https://support.google.com/mail/?p=ReceivingRatePerm p131si8414989oif.118 - gsmtp (in reply to RCPT TO command)

System Error

This bounce reason is classified when a bounce occurs due to a system error on the recipient's mail server, such as a connection failure to the LDAP server. 

<kijitora@example.net>: 
Unable to contact LDAP server. (#4.4.3)I'm not going to try again; this
message has been in the queue too long.
  • This domain's DNS violates RFC 1035.
  • Several matches found in Domino Directory
  • delivery to file forbidden
  • delivery to pipe forbidden
  • 550 5.2.0 RESOLVER.ADR.BadPrimary
  • 550 5.1.0 RESOLVER.ADR.InvalidInSmtp
  • 550 5.1.4 RESOLVER.ADR.Ambiguous
  • 451 Temporary local problem - please try later (in reply to end of DATA command)
  • Unable to contact LDAP server. (#4.4.3) I'm not going to try again;
  • 550 5.3.5 <kuroneko@example.org>... Internal System Error
  • 500 Remote server does not support TLS (state 6).

System Full

This error is returned when the recipient's mail server's disk is full. This indicates that the recipient host cannot receive any more emails. In the internal process of bounce email processing performed by Sisimai, this reason is determined for emails with a "5.3.1" or "4.3.1" value in the "Status:" field.

  • Requested action not taken: mailbox unavailable (not enough free space)
  • 452 4.4.5 Insufficient disk space; try again later

Too Many Connections (toomanyconn)

When a large number of connections are made to the recipient's SMTP server at the same time, new SMTP connections may be temporarily rejected. In such cases, the bounce email returned will be classified into this bounce reason by Sisimai. 

<kijitora@example.ne.jp>: host mx02.example.ne.jp[192.0.1.20] said:
452 4.3.2 Connection rate limit exceeded. (in reply to MAIL FROM command)
  • 550 5.5.3 RESOLVER.ADR.RecipLimit
  • 452 4.3.2 Connection rate limit exceeded. (in reply to MAIL FROM command)

Others

This is a list of other reasons, or reasons that Sisimai could not identify.

Delivered (beginning with v4.16.0)

This reason does not indicate an error, but rather that the sent email was successfully delivered to the recipient. Sisimai sets the "reason" value to delivered if the "Status:" field of the bounce email starts with "2".

This reason is not included in the decoded results by default. To include records with "delivered" in the decoded results, specify the delivered option as an argument to the rise() and dump() methods of the Sisimai class, as shown in the following sample code. 

Final-Recipient: rfc822; kijitora@neko.nyaan.jp
Action: deliverable
Status: 2.1.5
Diagnostic-Code: SMTP; 250 2.1.5 OK
Perl
#! /usr/bin/env perl
my $v = Sisimai->rise('/path/to/mbox', 'delivered' => 1);
my $r = Sisimai->dump('/path/to/mbox', 'delivered' => 1);
my $d = Sisimai::Fact->make('data' => $q, 'delivered' => 1);
Ruby
#! /usr/bin/env ruby
v = Sisimai.rise('/path/to/mbox', delivered: true)
r = Sisimai.dump('/path/to/mbox', delivered: true)
d = Sisimai::Fact.rise(data: q, delivered: true)

Vacation

This reason indicates that the recipient is unable to receive emails, possibly due to being on vacation. Bounce emails with this reason are sent by an autoresponder program. This bounce reason was implemented in Sisimai 4.1.28 and is not implemented in bounceHammer. Additionally, bounce emails with "vacation" as the reason are no longer decoded by default since Sisimai 5.0.0. 

I am out of the office until 05/01/2010.

I am of the office returning 5th Jan

Syntax Error (Beginning with v4.17.0)

This error indicates that the recipient's mail server did not recognize the SMTP command sent by the sending mail server. This bounce reason was implemented in Sisimai v4.17.0.

  • 503 Improper sequence of commands
  • 504 Command parameter not implemented

On Hold

When sending emails through some webmail services, and the email encounters an error, the bounce email may be returned with the error details removed. In such cases, it is known that some error has occurred, but the information necessary to identify the reason is missing, so Sisimai will withhold the determination of the bounce reason.

Undefined

If there are no error messages, response codes, delivery status codes, or any other information necessary for Sisimai to determine the bounce reason, the bounce reason will be set to "undefined".