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:
The following Protocol checks are activated in the config:Host or domain
name not found. Name service error for name=source.my.domain.com type=A: Host not found
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?