Equisys technical notes

Technical guidance, explanations and fixes for our products

FIX: Exchange Online Email Gateway stopped working with Basic Authentication



This Zetafax technical note applies to:

  • Zetafax Server version 17.5 and later
  • Exchange Online
  • Windows Server 2012 and later


As part of configuring Zetafax Exchange Online connector you are required to test the connection to your Exchange Online account. When testing the connection an error message is displayed "Connection to Exchange Online Failed. Check credentials and connectivity to Exchange."

Or when the Zetadax Server is running there are errors from the email gateway. "Unable to connect to Exchange Online. Check credentials and connectivity to Exchange"

This will affect all customers using the Exchange Online email gateway with Basic Authenticaton.


The Basic Authentication method (username/password) used previously to connect with Exchange Online has been disabled by Microsoft and has been replaced by the more secure Modern Authentication (OAuth2).


A hotfix is available to resolve this issue. Please contact Equisys technical support for more information.


This behaviour was corrected in the update detailed above.

Last updated: 18th March 2022  (MP/NT) 

Keywords: Exchange Online, Legacy Basic Authentication, OAuth2

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