SMTP basic authentication connections going away

[Tony Redmond]

Microsoft is doing its level best to remove SMTP basic authentication from Exchange Online as quickly as possible. Basic auth for SMTP connections will disappear gradually as time goes by. Tenants can make accounts more secure by removing SMTP authentication from accounts, something that Microsoft will do in the future when these connections are not used. An exception exists (for now) for SMTP client submissions, but these might also be affected in the future.

https://www.petri.com/microsoft-plans-disable-smtp-auth-exchange-online

[#2]

@Tony Redmond 

We have certain apps mailboxes which works on IMAP. We were planning to leverage o365 and migrate those mbxs to Office 365 by enabling IMAP for those mailboxes in office 365.

So, as per Microsoft's plan, would it be a problem for us after the migration?

[#3]

@thetechguru IMAP is a mail access protocol, so you use it to download messages from a mailbox. That will continue to work as Microsoft is developing modern authentication for IMAP (Oauth). I don't know when this will be available, but it is coming. SMTP is used to send messages, so you need to use it in conjunction with IMAP. Make sure that the accounts used by the app mailboxes are enabled for authenticated SMTP connections and stay up to date with developments in this field. And do lots of testing...