Mailing List Message #106915
From: Lyle <>
Subject: Re: 550 server without authentication error
Date: Wed, 1 Aug 2018 09:32:24 -0500
To: CommuniGate Pro Discussions <>

Another possibility is lack of DKIM or SPF records.  Some consider that 'lack of authentication', although I would not call it that.

But I agree with Mark, it's probably a misconfiguration on their part.

Lyle Giese

LCR Computer Services, Inc.

On 07/31/18 22:39, Mark Strawcutter wrote:

Since you've only seen it with one domain, there's a good chance that domain's inbound servers are misconfigured/misbehaving.


From: CommuniGate Pro Discussions <> on behalf of DUDLEY Paul <>
Sent: Tuesday, July 31, 2018 11:04 PM
To: CommuniGate Pro Discussions
Subject: 550 server without authentication error

We are using CommuniGate version 6.2.0. We have the outgoing SMTP setting set to send directly to the recipient.

Some emails are failing to be sent because of a “550 server without authentication error” refusal by the destination mail server.

What can I check as far as SMTP authentication goes within CommuniGate that may fix this problem?

I have only seen it so far with one destination mail domain.



Paul Dudley

0412 257 603



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