I’d got multiple SMTP transports on my postfix server, but one of these send’s newsletters,
As we already seen this in real life of an mailadmin some servers got rate-limit’s setup, so only a specific
amount of mail is accepted in a specific timeframe.
To get these masses sent to these destinations in a adequate timeframe we need a fallback relay.
Due to the configuration of the destination server these will accept mails from other client IP’s than
the rate-limited server is and they would send an 450 temporary error.
Long speech short sin.
Here as always my config snippet from postfix master.cf (somewhere at line 40):
smtp unix - - - - 50 smtp -o smtp_fallback_relay=relay01.bla.com
No magic. Really? DONT FORGET THE S**** TABSTOP IN FRONT of "-o smtp_fallback_relay="
Otherwhise you gonna get this:
postfix/master: fatal: /etc/postfix/master.cf: line 40: bad transport type: smtp_fallback_relay=relay01.bla.com
Due to this litte config mistake a new grey hair in my beard will gonna grow.