dovecot snarfing does not work on 20.04

[Dr. Uwe Meyer-Gruhl]

Description: Ubuntu Focal Fossa (development branch)
Release: 20.04
Package: dovecot (2.3.7.2-1ubuntu3)

Problem:

When using "snarf", the dovecot version delivered with 20.04 (Focal Fossa) does not work correctly. Snarfing is used to get new mail from /var/mail/%u to ~/mail/mbox (INBOX).

Mail content from the incoming mail directory does not get snarfed into the INBOX. Thus, no new incoming mail is ever detected.

This works fine with 18.04 which employs dovecot 2.2.32.2, but there seems to be no indication that something changed upstream, so I am at a loss at what causes this. When I enable debug output, I can even see that the snarf plugin is active.

When I install older dovecot-core, dovecot-popd3d and dovecot-imapd from 18.04 into 20.04, everything works as usual.

The relevant portion of my configuration is:

mail_location = mbox:~/mail/:INBOX=~/mail/mbox:INDEX=MEMORY
mail_plugins = snarf notify zlib

namespace snarf {
       prefix = ~~snarf/
       separator = /
       location = mbox:/run/dovecot/empty:INBOX=/var/mail/%u:INDEX=MEMORY
       list = no
       hidden = yes
}

plugin {
       snarf = ~~snarf/INBOX
}

[Dr. Uwe Meyer-Gruhl (meyergru)]

My bad: It does not work with the current dovecot 2.3.10 from the official repos, either.
Thus, it is an upstream bug.

I have found how to solve the problem:

mail_location = mbox:/home/%u/mail/:INBOX=/home/%u/mail/mbox:INDEX=MEMORY
mail_plugins = snarf notify zlib

namespace Snarf {
       prefix = ~~Snarfbox/
       separator = /
       location = mbox:/run/dovecot/empty:INBOX=/var/mail/%u:INDEX=MEMORY
       list = no
       hidden = yes
}

plugin {
       mbox_snarf = /home/%u/mail/mbox
       snarf = ~~Snarfbox/INBOX
}

[Dr. Uwe Meyer-Gruhl (meyergru)]

Not a bug in Ubuntu