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550 access denied invalid helo name exim

How to resolve “550 Access denied – Invalid HELO name” error from Outlook (0x800ccc78), Windows Mail, etc in DirectAdmin Exim mail servers

The mail user reports the error:

Task – Sending reported error (0x800CCC78): ‘Cannot send the 
message. Verify the email address in your account properties. The server 
responded: 550 Access denied – Invalid HELO name (See RFC2821

Corresponding entry in Exim logs say:

2014-09-24 07:06:31 [] rejected MAIL 
<>: Access denied - Invalid HELO name (See RFC2821

At Bobcares help desk support services, this is a common error we see in DirectAdmin shared hosting servers. Strict anti-spam rules or lack of SMTP authentication usually cause this error.


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Given below are a few scenarios we’ve encountered, and the solutions we provided for them. (more…)