Sisimai: Mail Analyzing Interface

Release Notes

Sisimai 5.8.0

2026/11/11

Sisimai 5.8.0 has been released. Main changes in this version include limiting the maximum size of email data: in-memory data from a variable, or STDIN to 2GB, and caps each individual email at 64MB, for memory protection. Perl at the beginning of each item, changes in the Ruby version of Sisimai are indicated by Ruby, and changes in the Go version of Sisimai are indicated by Go.

And then, Sisimai 5 includes many changes that are not compatible with Version 4, so please check the Perl or Ruby version of your environment before installing or upgrading.

Email Data Size Limits

  • Go Perl Ruby Limit the maximum email data size for memory protection. #487 #699 #472
    • The total size of input data (UNIX mbox, memory, or STDIN) is limited to 2GB.
    • Each individual email message (in Maildir/, UNIX mbox, memory, or STDIN) is limited to 64MB.

Security Fixes

  • Go Perl Ruby Add invisible/control character check to Makefile to prevent Trojan Source attacks. #439 #687 #458
  • Go Perl Ruby Check that the return value of rfc5322.Part() is an empty array or not. #450 #691 #463
  • Ruby Avoid RFC3464 crashes on empty or truncated attached messages. Thanks to @azranel. #462
  • Go Prevent potential infinite loop in mail.readMailbox() when scanning long lines. #469
  • Go Fix conditional logic in mail.listMaildir() function to properly exclude subdirectories. #470
  • Go Fix mbox email splitting bug when reading from STDIN or string payload. #484

Other Tiny Code Improvements

  • Go Perl Ruby The value of feedbackId returned from Amazon SES is set to the FeedbackID field. #427 #694 #467
  • Go Sisimai no longer depends on fmt package. #458

MTA modules and Error message patterns