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rated 0 times [  2] [ 0]  / answers: 1 / hits: 2342  / 2 Years ago, mon, september 5, 2022, 12:01:35

I have setup an intranet email system using postfix, dovecot and squirrel mail, Which is working fine, I can send and receive mail to all users on the system. I presume that the issue is in the postfix configuration, because when I configure Thunderbird to send mail I am getting the following error:



An error occurred while sending mail. The mail server responded:  4.1.8 <[email protected]>: Sender address rejected: Domain not found. Please check the message recipient [email protected] and try again.


Also here is the relevant syslog entries:



NOQUEUE: reject: RCPT from host1.intranetdomain.com [More Information] [192.168.11.1 [More Information] ]: 450 4.1.8 <[email protected]>: Sender address rejected: Domain not found; from=<[email protected]> to=<[email protected]> proto=ESMTP helo=<[127.0.0.1 [More Information] ]>


I have configured MX records on the DNS server and they respond appropriately when I query them for those MX records, so I do not think that is the issue. I think that my issue is caused by the default configuration of:



smtpd_recipient_restrictions = reject_unknown_sender_domain, reject_unknown_recipient_domain, reject_unauth_pipelining, permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination 

smtpd_sender_restrictions = reject_unknown_sender_domain


Since this is on an internal network and it will not be exposed to the internet as a whole which options can I remove safely?


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smtpd_sender_restrictions = reject_unknown_sender_domain


Don't accept mail from domains that don't exist. (source)





reject_unknown_recipient_domain


Reject the request when Postfix is not final destination for the recipient domain, and the RCPT TO domain has 1) no DNS A or MX record or 2) a malformed MX record such as a record with a zero-length MX hostname (Postfix version 2.3 and later) (source)





If you need to change both to make it work, will you have to fake the sender domains in your local DNS or add them to the /etc/hosts file on the server. From the explanation, postfix will reject it if it can't look up the domain.



For the second, should you be fine with adding the receiver domain in the servers /etc/hosts file. Explaination: Dovecot use virtual transport, and thus Postfix is, as i have understood it, not considered the final destination and you will need to have proper "path" to the destination. How? Add a DNS A record (to the servers host file) or a proper MX record to your local DNS.





For your question: Yes, you can remove safely, but that will turn off the filters refereed above.


[#28538] Monday, September 5, 2022, 2 Years  [reply] [flag answer]
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calronze
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