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SMTP authentication unsuccessful error – How to resolve

by | Oct 28, 2021

Stuck with SMTP authentication unsuccessful error? We can help you.

As part of our Server Management Services, we assist our customers with several cPanel queries.

Today, let us see how our Support techs resolve it.

How to resolve SMTP authentication unsuccessful error?

‘Authentication Unsuccessful‘ error can occur when a Microsoft 365 user tries to send emails whilst IMAP is select as the server type.

This problem occurs because SMTP authentication is block by default for security reasons inside Microsoft 365’s settings by any company making use of it.

Use the Exchange protocol which is part of our Business plan to use Microsoft 365 accounts within Mailbird– ultimately.

In order to fix the ‘Authentication Unsuccessful‘ error, you need to have Authenticated SMTP enabled in your organization’s settings within Microsoft 365.

This setting can only be enabled only by the organization’s Administrator.

Today, let us see the steps followed by our Support Techs to resolve it

1. Firstly, go to the ‘Microsoft 365 Admin Center’
2. Next, go to Users and then Active users to select the user for whom you want to enable this setting
3. Then go to Mail, and then Manage email apps
4. Make sure Authenticated SMTP is enabled and then save changes.

In order to enable Authenticated SMTP for an entire organization, here are our suggested steps:

1. Firstly, log into the organization via PowerShell
2. Execute the following “Set-TransportConfig -SmtpClientAuthenticationDisabled $false“.

[Stuck in between? We’d be glad to assist you]


In short, today we saw steps followed by our Support Techs to resolve SMTP authentication error.


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