Apologies for "bumping" this post, but I had the same issue and was able to find a resolution that seems to be worth documenting.
I, too, followed the guide at http://www.faqforge.com/linux/contro...n-ispconfig-3/
in order to disable Amavis and ClamAV on a low-memory server.
Of course, at the time, I did not absorb the most important piece of the article, which is at the bottom (should it be moved to the top?):
The changes in postfix main.cf will get overwitten by a ispconfig software update when you select to reconfigure services during upadte, so you should comment out the lines again after you install a ispconfig update.
After performing ISPConfig3 and OS updates, mail delivery ceased to function. I'm not sure if I elected to reconfigure services, but if that is the default, then I probably did.
Issuing the command
# egrep '(warning|error|fatal|panic):' /var/log/mail.log | more
made it apparent that the problem was indeed Amavis:
postfix/qmgr[XXXX]: warning: connect to transport private/amavis: Connection refused
I noticed that the lines I had commented per the KB article cited above were re-added at the bottom:
content_filter = amavis:[127.0.0.1]:10024
receive_override_options = no_address_mappings
So, I re-commented the lines and restarted Postfix.
Still, the problem was not resolved... until I re-queued all of the previously-queued mail:
I'm no expert in this regard, but it seems that Postfix may have been using cached configuration files (even though I had restarted the service several times after re-commenting the lines in question), as evidenced by
# grep -r "amavis" /etc/postfix
/etc/postfix/master.cf:#amavis unix - - - - 2 smtp
/etc/postfix/main.cf:#content_filter = amavis:[127.0.0.1]:10024
/etc/postfix/main.cf~:#content_filter = amavis:[127.0.0.1]:10024
/etc/postfix/main.cf~:content_filter = amavis:[127.0.0.1]:10024
/etc/postfix/master.cf~:#amavis unix - - - - 2 smtp
/etc/postfix/main.cf~3:#content_filter = amavis:[127.0.0.1]:10024
/etc/postfix/main.cf~2:#content_filter = amavis:[127.0.0.1]:10024
/etc/postfix/main.cf.bak:#content_filter = amavis:[127.0.0.1]:10024
/etc/postfix/main.cf.bak:content_filter = amavis:[127.0.0.1]:10024
Any expert comments as to why re-queuing the undelivered mail resolved the issue are appreciated.