How to debug qmail with simscan, clamav and spamassassin

How to debug qmail with simscan, clamav and spamassassin?

Qmail sends this error "451 mail server temporarily rejected message (#4.3.0)" and all messages are rejected but in logs there is nothing suspicious. How can this be debugged?

You need to edit your /etc/tcp.smtp and add some debug variables. Normally the file looks like this:

127.0.0.1:allow,RELAYCLIENT="",QMAILQUEUE="/usr/sbin/simscan"
:allow,QMAILQUEUE="/usr/sbin/simscan"

Modify your settings like this:

127.0.0.1:allow,RELAYCLIENT="",QMAILQUEUE="/usr/sbin/simscan"
:allow,SIMSCAN_DEBUG="2",NOP0FCHECK="1",QMAILQUEUE="/usr/sbin/simscan"

Make sure that QMAILQUEUE points to the right path of simscan.
Recompile your /etc/tcp.smtp

# tcprules /etc/tcp.smtp.cdb /tmp/t.tmp < /etc/tcp.smtp

Now logs are filled with needed information and you can debug your problem. Remember to remove debugging after the problem.

Example debug output:

# tail -f /var/log/qmail/smtpd/current
@4000000050f019b9351afa74 simscan: cdb looking up
@4000000050f019b9351c2f0c simscan: cdb for  found clam=yes,spam=yes,spam_hits=4.9
@4000000050f019b93521b51c simscan: pelookup clam = yes
@4000000050f019b93521b904 simscan: pelookup spam = yes
@4000000050f019b93521c0d4 simscan: pelookup spam_hits = 4.9
@4000000050f019b93521c8a4 simscan: starting: work dir: /var/qmail/simscan/1357912495.891056.16277
@4000000050f019bb13bc6804 simscan: pelookup: called with xxxasd@safds.com
@4000000050f019bb13bc9acc simscan: pelookup: domain is safds.com
@4000000050f019bb13bc9eb4 simscan: cdb looking up safds.com
@4000000050f019bb13bcae54 simscan: pelookup: local part is gxxxx
@4000000050f019bb13bccd94 simscan: cdb looking up xxxasd@safds.com
@4000000050f019bb13bce8ec simscan: pelookup: called with gxxxx@stemo.bg
@4000000050f019bb13bcfc74 simscan: pelookup: domain is stemo.bg
@4000000050f019bb13bd005c simscan: cdb looking up stemo.bg
@4000000050f019bb13bd1bb4 simscan: cdb for stemo.bg found clam=yes,spam=yes,spam_hits=5.7
@4000000050f019bb13bd2f3c simscan: pelookup clam = yes
@4000000050f019bb13bd2f3c simscan: pelookup spam = yes
@4000000050f019bb13bd3324 simscan: pelookup spam_hits = 5.7
@4000000050f019bb13bd46ac simscan: pelookup: local part is gxxxx
@4000000050f019bb13bd46ac simscan: cdb looking up gxxxx@stemo.bg
@4000000050f019bb13c65ecc simscan: calling clamdscan
@4000000050f019c110b86b1c simscan: fatal error executing clamdscan
@4000000050f019c110ba6304 simscan: exit error code: 71