Recently we at ITEG IT-Engineers GmbH are moving the e-mail customers inherited from IBCL e.U. from a 9 year old very legacy setup to a new setup based on postfix, postfixadmin, dovecot, and roundcube.
Unfortunately postfixadmin was missing a nice feature for vacation messages: It was unable to include the subject of the original message in the vacation message.
As our users are accustomed to this behaviour, we have developed an according patch for vacation.pl and submitted it to the postfixadmin project as patch 3536134.
The patched vacation.pl basically replaces any '$SUBJECT' (that is, a dollar sign and the word subject in upper case letters) in the vacation mail subject template with the subject of the original e-mail.
For example: If the vacation mail subject is set to 'Re: $SUBJECT', the vacation mail gets the same subject as a common reply mail created by the recipient using an e-mail application.
To use this as the default subject template, the langauge file has to be changed.
This is from our
$PALANG['pUsersVacation_subject_text'] = 'Re: $SUBJECT';