[Dovecot] Dovecot deliver discards emails (mail loss)

[Justin McAleer]

Steffen Kaiser wrote:
>  msgid=<200705080749.l487nclf029596 at ux-2s11-9.inf.fh-bonn-rhein-sieg.de>: 
> Return-Path missing, rejection reason: Not enough disk space
> May  8 09:49:53 ux-2s11-9 sendmail[29618]: l487nclf029596: to="| 
> /etc/mail/runde", ctladdr=dvtest (31045/102), delay=00:00:15, 
> xdelay=00:00:00, mailer=prog, pri=120033, dsn=2.0.0, stat=Sent
>
>

Was the return-path of that message indeed empty/missing as indicated? 
Can you show the entire log history for message id l487nclf029596? Of 
course, if there was no return-path, then no bounce would be generated.