Forum Discussion
Problem with SMTP Authentication (Microsoft Support Can't handle)
Hi, We had a problem with SMTP authentication for our tenant M365. Here is the brief story.... It can authenticate formerly but can't authenticate suddenly starting from 5th December 2022. Afte...
Check the per-mailbox settings, as they override the tenant-wide one:
Get-CASMailbox email address removed for privacy reasons | select SmtpClientAuthenticationDisabled
Similarly, check for the presence of any auth policies that might be blocking SMTP:
Get-AuthenticationPolicy | select Name, AllowBasicAuthSmtp
You can also try using the legacy endpoint: https://learn.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/opt-in-exchange-online-endpoint-for-legacy-tls-using-smtp-auth
Get-CASMailbox email address removed for privacy reasons | select SmtpClientAuthenticationDisabled
Similarly, check for the presence of any auth policies that might be blocking SMTP:
Get-AuthenticationPolicy | select Name, AllowBasicAuthSmtp
You can also try using the legacy endpoint: https://learn.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/opt-in-exchange-online-endpoint-for-legacy-tls-using-smtp-auth
- Hi Vasil,
Thanks for your participation and help.
As of now, the problem is fixed by turning on SMTP Authentication in Admin panel > Settings > Org Settings > Modern Authentication > check "Authenticated SMTP (Used by POP and IMAP clients to send email messages)" with the help of Microsoft assistant. I have no idea since they have done this step with previous MS assistant, and it is not working before. That's why they did tried with PowerShell. But strangely, it is working back after turning on the above checkbox.
Anyway, it is good for us and thank you so much.
Have a great day ahead
