10G mails use 90G on disk

[Aki Tuomi]

> On 29/01/2021 13:24 Markus Schönhaber <dovecot at list-post.mks-mail.de> wrote:
> 
>  
> 29.01.21 11:46 +0100, Aki Tuomi:
> 
> >> On 29/01/2021 12:41 Markus Schönhaber <dovecot at list-post.mks-mail.de> wrote:
> >>
> >>  
> >> Hello,
> >>
> >> on a system I administer the disk where Dovecot's mailstore (mdbox)
> >> resides got filled up to the brim although the combined quotas for the
> >> users are much smaller than the disk's capacity.
> >>
> >> For one user I see the following:
> >>
> >> doveadm quota get -u <USER>@<DOMAIN>
> >> Username         Quota name Type       Value    Limit
> >>                           %
> >> <USER>@<DOMAIN>  User quota STORAGE 10231248 20971520
> >>                          48
> >> <USER>@<DOMAIN>  User quota MESSAGE    11176        -
> >>                           0
> >>
> >> So this user has used ~10G of his 20G quota. But looking at the space
> >> used on disk:
> >>
> >> # du -hs /var/spool/vmail/mail/<DOMAIN>/<USER>/storage/
> >> 90G     /var/spool/vmail/mail/<DOMAIN>/<USER>/storage/
> >>
> >> What might be the reason that mail size and disk space used differ so much?
> >> And most of all: how can I prevent that from happening?
> 
> > mdbox format requires you to periodically run
> > 
> > doveadm purge -u user
> > 
> > to cleanup deleted mails from the mdbox storage. mdbox has feature that you can use mail_location mdbox_deleted to access any deleted emails if you need to recover them, but it also requires you to purge the storage now and then.
> 
> Thanks for your answer, Aki!
> I will configure a cron-job to purge the user's mailstore.
> 
> Nevertheless, since this is a very low volume server and the user in
> question only sends and receives a few dozen mails, weighing a hand full
> of MB, per day, I'm at a loss to understand how it's possible that in
> the user's mailstore 80G of deleted but not purged mail can pile up in
> just about a week(!).
> This has happend a couple of times during the last month. And after it
> happened the last time (8 days ago), I had manually purged the user's
> mailstore reducing ist's size back to the ~10G that are reasonable.
> Since then it has grown to the 90G I mentioned above.
> 
> So, if you have any idea what to check or what measures to take to help
> me find out what's happening there, that woud be great!
> I'll start to log the mailstore size regularly to be able follow the
> growth over time but maybe there's something I could tell Dovecot to do...
> 
> -- 
> Regards
>   mks

Using mail_log plugin is always very recommended,

https://doc.dovecot.org/configuration_manual/plugins/mail_event_logging/

Aki