Hi, I'm new to dovecot but as I see in mailinglist archive this issue is old and I didn't find this in archive.

One of cuplrits (I believe not the only possible) is spamassassin. It's added headers make exactly the difference between S value and filesize. Probably it's in the way emails are processed in "manufactory" of Qmail+Vpopmail+Spamassassin but now I'm not able to say how can it be repaired.

As mentioned above I'm using solution with Qmail+Vpopmail+Spamassassin+Dovecot, my Dovecot version is 2.2.26.0.

Libor Pavlík