concering dovecot logging

[Rajesh M]

hi

had a question concerning dovecot lda logging.

deliver_log_format = From:<%f>-<%e> :: Subject:<%s> :: Status:<%$> ::
MsgID:<%m> :: Size<%p> :: vSize<%w>

am getting %e ie envelope sender as MAILER-DAEMON in the logs

Sep 11 08:35:50 lda(noc at xxx.com): Info: sieve: From:<bmmsro0612 at xxx.co.in>-<MAILER-DAEMON> :: Subject:<Fw: ccccccn> :: Status:<forwarded to <nocforward at yyyyy.com>> :: MsgID:<<OFBECDF3FA.57B3772C-ON65258198.00111392-65258198.00111394 at xxx.co.in>> :: Size<12497> :: vSize<12687>

what could be the reason ?

thanks,
rajesh