Problem with SMTP Authentication (Microsoft Support Can't handle)

Copper Contributor



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. After we have digested some documents from Microsoft, SMTP protocol still can authenticate even after deprecation of Basic Authentication. Ref: Basic Authentication Deprecation in Exchange Online – September 2022 Update - Microsoft Community Hu...


We have turned on Multifactor authentication in our tenant but already turned off the security default in Azure AD since it can impact to SMTP protocol to send out the message if ON.


Then we have opened the ticket to Microsoft and the support agent provided us to try the following method....

1) enable SMTP auth in active users > mail apps > check SMTP authentication

2) enable SMTP auth using PowerShell commands in exchange online 


After running some command as instruct, we got the following result

Get-TransportConfig | Format-List SmtpClientAuthenticationDisabled

SmtpClientAuthenticationDisabled : False

The above result means SMTP is enabled. However, we still can't authenticate


We have tested with outlook 2016 - IMAP configuration.

incoming : 993/SSL

outgoing :


Note: we can understand that incoming mail won't work since we have disable Basic Authentication and incoming should got error but outgoing with SMTP should work. 

As I mentioned earlier, it works fine before 5th of Dec 2022.


My question is that, is there any way to fix this issue since it still can't handle be microsoft agent with wired solution which won't work


Why Microsoft didn't care including the support agent can't handle long time.


Thank you

2 Replies
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:
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