[SOLVED] DNS lookups for my trusted networks

[mk60528]

I'm trying to send emails from the internal network to a mailbox which is hosted on the Zimbra server. But the emails are bounced with the following message:

Host or domain
name not found. Name service error for name=source.my.domain.com type=A: Host not found

The following Protocol checks are activated in the config:
reject_invalid_hostname
reject_non_fqdn_hostname
reject_non_fqdn_sender

When I send the same email to an external recipient outside of Zimbra and our networks, the email is accepted. The problem only occurs when sending to a mailbox on our Zimbra server.

I wonder why Zimbra checks the A record of the sending host, and is it possible to turn off DNS lookups for hosts which are part of the MTA trusted networks?

[phoenix]

I wonder why Zimbra checks the A record of the sending host,

It's a postfix requirement. Have you set-up a Split DNS? If you haven't then you need one if your behind a NAT router or firewall, if you have then go to that article and run all the commands in the 'Verify...' section to check your settings.

[mk60528]

Thanks for you quick reply. Yes - this is a DNS problem. But I found out that it's the DSN which is discarded, since the sender domain doesn't have any A records for this host which sent the emails.

The original problem was an alias domain. Emails couldn't be accepted for this alias domain, so postfix generate a DSN. I have fixed the original problem.

Thanks for you help!