Verify Receivers

[kevin]

Good day

I have installed PMG and i ineed to understand what the setings Reject Unknown Senders and Reject Unknown clients do.

In my case we have a mail server on which email accounts are resident for our domain. The PMG server is not the final destination.

Also the Verify receivers option what are the implications of setting it to yes or setting it to not

 

[Stoiko Ivanov]

Reject Unknown Senders

sets 'reject_unknown_sender_domain' in postfix' main.cf 'smtpd_sender_restrictions' setting - see http://www.postfix.org/postconf.5.html#reject_unknown_sender_domain

Reject Unknown clients

sets 'reject_unknown_client_hostname' also for 'smtpd_sender_restrictions' - see http://www.postfix.org/postconf.5.html#reject_unknown_client_hostname

Also the Verify receivers option what are the implications of setting it to yes or setting it to not

see http://www.postfix.org/ADDRESS_VERIFICATION_README.html
It makes postfix 'verify' the recipient address for inbound mail by connecting to your downstream server and trying to send a mail there:
* if the server answers with 250 to the RCPT TO command the verification is successfull
* if it answers with 4xx or 5xx to RCPT TO the mail get rejected

in both cases the results are cached on PMG to keep traffic low - see http://www.postfix.org/ADDRESS_VERIFICATION_README.html#caching

I hope this helps!

 

[kevin]

Now this leads me to the next question.

If i have verify receivers set to yes the incoming mail does not come through. in some instances i get the 550 message sometimes i do not. If i set it to no the incoming mail comes through.

what could be the issue here

 

[Stoiko Ivanov]

The logs (/var/log/syslog or the journal (man journalctl)) should provide more insight in what is going wrong

 

[kevin]

the reason is the users are there. maybe i will need to look into the downstream server

 

[Stoiko Ivanov]

the reason is the users are there.

then recipient verification should accept the mail and forward it to the downstream server

 

[kevin]

Now in my case strangely it is not. If i do a tail -f /var/log/mail.log the message that comes out is Recipient address rejected undeliverable address host ["host ip"] says 573 double-bounce@"hostname of PMG server" unknown user account in reply TO MAIL FROM: command

 

[Stoiko Ivanov]

Now in my case strangely it is not. If i do a tail -f /var/log/mail.log

on which server do you do the tail -f?

["host ip"] says 573 double-bounce@"hostname of PMG server" unknown user account in reply TO MAIL FROM: command

if "host ip" is the ip of the downstream server then the downstream server does not accept mail from your PMG
(in that case maybe related to the double-bounce localpart PMG/postfix uses for address verification probes)

-> check the downstream servers configuration and make sure it accepts mails from PMG