On 1/20/26 2:48 PM, Wietse Venema via Postfix-users wrote:
Jamie McClelland via Postfix-users:
Hi all,
I carefully read a thread from a few years ago about warming up IP
addresses using Postfix:
https://www.mail-archive.com/[email protected]/msg97100.html
One answer was to use a database lookup
(https://www.mail-archive.com/[email protected]/msg97102.html)
and another answer was to use smtpd_recipient_restrictions and randmap
(https://www.mail-archive.com/[email protected]/msg97107.html).
However, both answers *seem* to base the rate limiting on the
destination domain name, not the destination MX server. Since a
considerable amount of email goes to Microsoft and Google from custom
domain names, this shortcoming means the rate limiting will let a lot
more email go to Google and Microsoft than intended.
Indeed, the Postfix scheduler is driven by destination domain
and it does not look up MX records. That was nt a proboem
when the scheudler was designed and implemented.
There is a workaround (solution?) that uses check_recipient_mx_access
and content filter support:
/etc/postfix/main.cf:
smtpd_something_restrictions =
...
check_recipient_access lmdb:/etc/postfix/mx-filter
...
/etc/postfix/mx-filter:
outlook.com filter outlook-smtp:
google.com filter google-smtp:
...
/etc/postfix/master.cf:
outlook-smtp ...same fields as generic 'smtp' client...
google-smtp ...same fields as generic 'smtp' client...
Thank you for the quick response pointing me in a different direction.
Since I've already written the TCP tables program that rate limits how I
want, do you see any problems with this modified approach that uses TCP
Tables?
/etc/postfix/main.cf:
smtpd_recipient_restrictions =
...
check_recipient_mx_address tcp:127.0.0.1:1234
...
The TCP Tables program would either respond with:
* DUNNO (if the program determines that the MX server can handle
receiving another message from this IP based on previous lookups)
* FILTER smtp:[warm.example.org] (if the MX server has received too
many email messages - warm.example.org uses round robin DNS with already
warmed up IP addresses)
Also, would check_recipient_mx_addres query just one MX record (the one
with the highest priority)?
jamie
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