You may encounter a message of this variant:
With Microsoft 365 accounts, the error can occur when a user tries to send an email, but the SMTP authentication is blocked inside the Microsoft 365 settings by the company.
Solution:
Your organization must enable Authenticated SMTP within the administrator settings. This will be through either Microsoft 365 Admin Center for a specific user/users or PowerShell if required for an entire organization.
KEY NOTE: For GoDaddy Microsoft 365 users it won't be possible to enable SMTP for individual users, but only for the whole organization through PowerShell.
Below are the suggested steps in order to enabler Authenticated SMTP for a Specific Account :
2. 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. First, log into the organization via PowerShell
2. Execute the following "Set-TransportConfig -SmtpClientAuthenticationDisabled $false".
For more details, please take a look at the following documentation provided by Microsoft: