Defect #31365

Issue subject may be broken if the subject field in the receiving email is split into multiple lines

Added by Go MAEDA 6 days ago. Updated 4 days ago.

Status:NewStart date:
Priority:NormalDue date:
Assignee:-% Done:


Category:Email receiving
Target version:Candidate for next minor release
Resolution: Affected version:


When you create issues via email, the subject of the created issue may be broken if the subject field in the original email is split into multiple lines like the following.

Date: Mon, 13 May 2019 13:39:29 +0900
Message-ID: <>
Subject: =?utf-8?B?zrHOss6zzrTOtc62zrfOuM65zrrOu868zr3Ovs6/z4DPgc+Cz4PPhM+Fz4bP?=
From: <>
To: <>
Content-Type: text/plain

Split bytes subject.

The subject should be decoded like this:


But the subject of the created issue will be the following:


This is due to the bug of mail gem (I tested in 2.7.1).

irb(main):001:0> puts'/tmp/split-bytes-subject.eml').subject
=> nil

The subject is not split at the boundary between characters but in the middle of bytes that composes a character and mail gem that parses emails does not properly handle such emails. The first line of the decoded subject field is "αβγδεζηθικλμνξοπρςστυφ\xCF" and the second line is "\x87ψω". The character "χ" is consists of two bytes 0xCF and 0x87. These two bytes span two lines. mail gem cannot handle such cases.

split-bytes-subject.eml - Email which reproduces the issue (332 Bytes) Go MAEDA, 2019-05-14 05:49

31365_mail_gem_broken_subject.patch Magnifier (2.38 KB) Yuichi HARADA, 2019-05-16 06:49


#1 Updated by Yuichi HARADA 4 days ago

The subject seems to be broken because Mail::SubjectField does not combine multiple lines of subjects into one line.

I created a monkey patch for Mail::SubjectField .

#2 Updated by Go MAEDA 4 days ago

  • Target version set to Candidate for next minor release

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