Table of contents
Issue:
The customer faced an error while testing the custom SMTP settings in the RH portal.
Step-by-step Solution
First, test the settings using a third-party tool “SMTP Tester Tool: Free tool to test your SMTP configuration.” Below is the video to show how to verify the SMTP settings in a third-party tool.
If the error persists, follow the solution below.
There are a few things you should check:
Use Exchange Online PowerShell to verify that authenticated SMTP submission (also known as SMTP AUTH) is enabled on the licensed mailbox that the application is using to connect to Microsoft 365 or Office 365:
In Exchange Online PowerShell, replace <EmailAddress> with the email address and run the following command:
PowerShell
Get-CASMailbox -Identity <EmailAddress> | Format-List SmtpClientAuthenticationDisabled
If the value is True, replace <EmailAddress> with the email address and run the following command to enable it:
PowerShell
Set-CASMailbox -Identity <EmailAddress> -SmtpClientAuthenticationDisabled $false
2. Disable multifactor authentication (MFA) on the licensed mailbox that's being used:
In the Microsoft 365 admin center, in the left navigation menu, choose Users > Active users.
On the Active users page, choose Multi-Factor Authentication.
On the multi-factor authentication page, select the user and disable the multifactor authentication status.
3. Disable the Azure Security Defaults by toggling the Enable Security Defaults to No:
Sign in to the Azure portal as a Security administrator or Conditional Access administrator.
Browse to Microsoft Entra ID > Properties.
Select Manage security defaults.
Set the Enable security defaults toggle to No.
Select Save.
4. Exclude the user from a Conditional Access policy that blocks Legacy Authentication:
Sign in to the Azure portal as a Security administrator or Conditional Access administrator.
Browse to Microsoft Entra ID > Security > Conditional Access.
In the policy that blocks Legacy Authentication, exclude the mailbox being used under Users and Groups > Exclude.
Select Save.
Reference