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 <firstname.lastname@example.org>: Sender address rejected: Domain not found. Please check the message recipient email@example.com 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 <firstname.lastname@example.org>: Sender address rejected: Domain not found; from=<email@example.com> to=<firstname.lastname@example.org> 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?