When using a issue reference like @[Issue #455]@ and configuring redmine to receive emails by polling a IMAP/POP3 account, the referenced ticket gets updated correctly.

Using this feature between companies which use the same scheme fails however as the parser will only extract the first number from subjects like "Re: [Issue #12333212] [Ticket #55893] Bandwidth limit", which will assign the content of the email to either the wrong issue or simply fail (when the issue does not exist).

The regexp for extracting the issue number is currently the following:

ISSUE_REPLY_SUBJECT_RE = %r{\[(?:[^\]]*\s+)?#(\d+)\]}

h2. Improvement

We'd propose to add a custom tag to this matching scheme so each installation can reference tickets in a unique way like this:

• "@Re: [ACME #88989] [JIRA #1231233312] Bandwidth limit@"
• "@Re: [ACME #12932] Bandwith limit@"

The tag should be configurable in the admin interface or similar, the regexp could be something like

ISSUE_REPLY_SUBJECT_RE = %r{[(?:[]]*(?:${tag})\s?)?#(\d+)]}i

which would allow for "@Re: [ACME #88899]...@" and "@Re: [ACME#88899]...@"