postfix checks email addresses of subdomains the server is not responsible

Hi team,
we have a setup, one of our email server is responsible for domain.com but not for sub.domain.com. If someone tries to send an email from [email protected] to [email protected] tihs email is transfered to our email server. But our email server rejects the email

NOQUEUE: reject: RCPT from mx.host.com[1.2.3.4]: 550 5.1.0 <[email protected]>: Sender address rejected: User unknown in relay recipient table; from=<[email protected]> to=<[email protected]> proto=ESMTP helo=<mx.host.com>

Again: sub.domain.com is not configured in our ISPconfig system.
domain.com is created as relay-domain - the email server is only a backup MTA for that domain.

Sending an email from <[email protected]> to <[email protected]> passes our email server w/o any problem. Any other email traffic is handled as expected from the server (filtering, anti spam, etc).

Any idea is welcome ;-)

Regards,
CMKS

 

Hey Till,
it rejects the email because of the sending email address - not the receipient. But the server only should check sending email addresses of domain it is responsible for. it is not responsilbe for that subdomain.

Have another look:
domain.com MX srv1.domain.com
sub.domain.com MX srv2.sub.domain.com

Send an email fom <[email protected]> to <[email protected]>

Erroneously srv1.domain.com rejects the email because it does not know the sender address <[email protected]>
But srv1 is not responsible for sub.domain.com in any way. So it can not know anything about sub.domain.com.

 

Great hint, that's the key:

Code:

# postconf -d | grep parent_domain_matches_subdomains
parent_domain_matches_subdomains = debug_peer_list,fast_flush_domains,mynetworks,permit_mx_backup_networks,qmqpd_authorized_clients,relay_domains,smtpd_access_maps

How can I update the postfix main.cf in a ISPconfig compatible manner? It should be peristent even when we install a new version of ISPConfig?