Filter of old Thunderbird installation interferes with lmtp/ Mail delivery / sieve

[Jürgen Gmach]

# 2.2.13: /etc/dovecot/dovecot.conf
# OS: Linux 4.9.25 i686 Gentoo Base System release 2.2
# pidgeonhole v0.4.3
# Thunderbird 3.0.4

impact
------
Emails, for which the filter applies, gets copied to the desired folder, 
but get kept in the inbox with deleted flag (in Roundcube you see them 
grayed out a bit, in Thunderbird they are not shown at all).

When the incoming email is from an internal mailing list (mailman), 
beginning with the user with the buggy Thunderbird all following emails 
of the internal users are flagged as deleted, but only if the user has a 
sieve file in their directory - no matter whether it is active or not.


After activating detailed logging the user with the "problematic" filter 
was found quickly.

The error is reproducible:
- install old Thunderbird version
- create filter
- write an email, which triggers the filter
-> email is flagged deleted but does not get deleted

Though, the user does not have a sieve file on our server, the filtering 
happened in the very same second when the email was delivered to the 
other colleagues.

Both Thunderbird and Pidgeonhole are outdated, so I am unsure if you are 
even interested in this bug report.

Fix
---
I made the user to update his Thunderbird version -> no more problems. 
Anyhow, a single "user interaction" should not be able to effect other 
mail accounts (ie Thunderbirds filter somehow disturbed the lmtp 
process).


-- 
Jürgen Gmach . juergen.gmach at apis.de . +49 9482 941545
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