Mailing List Message #106930
From: Patrick Sneyers <>
Date: Wed, 15 Aug 2018 15:56:37 +0200
To: CommuniGate Pro Discussions <>
X-Mailer: Apple Mail (2.3445.9.1)
> We are running CommuniGate Pro v6.2.0 on a Red Hat linux server. When we try to send emails to a specific external address, their mail system replies with the following delivery failure:
> Failed to deliver to ''
> SMTP module(domain reports:
> host says:
> 550 server without authentication.
> At this point in time this is the only external email domain that we are sending to which is reporting this problem.
> Are there any settings I can check on our CommuniGate Pro server?

Looks like a DNS issue to me.

MX records for are:

Your message should have gone to

It looks like CGP didn't find the MX records for
In that case CGP tries to send to the A-record, which, by the way, I find very annoying (I'm still hoping for a way to disable this "feature" - no MX = domain accepts no email to me).

The A record is listening on port 25, so some MTA is active there. But it's not set up to receive without SMTP authentication for
Hence te error.

Patrick Sneyers
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