Hello! I couldn't find any working solution for my problem online, but please don't yell at me if this question has been asked before. I'm using ISPConfig 3.1.1p1 on Debian 8 with Dovecot as IMAP server. I have configured a domain "xy . com" with a mailbox "foo@xy . com" and "bar@xy . com", the hostname of my server is "mail01 . foobar . com". Both mailboxes are only allowed to send emails, so "Enable receiving" is off for both of them, IMAP and POP3 are disabled. There is another (MS Exchange) mailserver configured for receiving emails, let's name it "mx01 . bigcompany . com". There is no MX record configured for mail01 . foobar . com. There is an MX record pointing to mx01 . bigcompany . com. When I send an email from "foo@xy . com" to "bar@xy . com" postfix replies with 550 5.1.1 <bar@xy . com>: Recipient address rejected: User unknown in virtual mailbox table; from=<foo@xy . com> to=<bar@xy . com> proto=ESMTP helo=<[...]> How can I tell postfix to disable local delivery for this domain? Sorry for the weird hostnames and email addresses, the forum thinks they are links and doesn't allow me to post links.
When you add an email domain in postfix, then postfix will always deliver locally to that domain, no matter where the MX record is pointing to. When you need an email account for sending only, then use a different domain name, even a non-existing, to create these smtp out accounts. Ensure that you do not enable "Reject sender and login mismatch" in server config.
