On 5/31/2019 1:48 AM, Stefan Bauer wrote:
Hi,
I'm running a pair of postfix-servers in different data-centers
(different ip networks) for outgoing-only delivery. once in a while
my providers /22 appear on public blacklists, so mails from my nodes
also gets rejected.
For this, i have now a third backup-instance in another data center
that is not visible to my users and only fairly with dummy mails
used to keep reputation up and good. Howto re-route traffic on
demand with postfix in case, ip-networks get blocked again?
How do others handle this?
Thank you.
Stefan
Much better to send all your mail via the ISP that doesn't get their
whole space blocked, rather than a crappy workaround.
For a crappy workaround, you can use smtp_reply_filter to turn 5xx
rejects due to blacklists into 4xx temp failures, then use
smtp_fallback_relay to send the temp failures to your backup server.
This will send other mail to the backup server, such as greylisted
mail or mail that temp fails for unrelated reasons. Try to make your
reply filter narrow enough that it doesn't transform rejects for
non-rbl reasons, such as unknown recipient.
http://www.postfix.org/postconf.5.html#smtp_reply_filter
http://www.postfix.org/postconf.5.html#smtp_fallback_relay
-- Noel Jones
