This is a problem we came upon while setting up the split MX (described
earlier on this list). On the the smtp gateway I have this in master.cf
smtp inet n - - - 20 smtpd
-o cleanup_service_name=pre-cleanup
-o smtpd_proxy_filter=127.0.0.1:10024
-o smtpd_client_connection_count_limit=10
-o content_filter=
# -o content_filter=127.0.0.1:10024
The proxy filter is amavis doing spamassassin. It's based on some docs I found
about pre queue insertion content inspection on postfix.org. The idea is to
eliminate backscatter.
The (well known) problem with this is that once the machine gets busy messages
start getting queued via the secondary MX, introducing additional delays. I
think it would be a killer feature of postfix if it started doing something
like this: once all the smtp processes (20 above) are in use switch to
accepting smtp connections but doing content filtering (e.g. similar to the
line commented out above). Is this already feasible in postfix?
Thanks for any replies
mimo
