To add to what has already been mentioned......
As you may know, there has been talk of completely removing basic authentication from O365/Exchange Online for the last couple of years. It was supposed to already have been done but got pushed back due to covid and such.
Currently, Exchange Online/O365 have put a deadline that as of October 2022, basic authentication will be permanently disabled moving forward.
Why this is important to us, is that our Exchange emailing in Dynamics GP 18.3 and prior, requires basic authentication to be enabled on Exchange, in order to authenticate.
This being said, since about Feb 2022, we've become aware that Exchange has been disabling basic authentication on some O365 tenants, in preparation of this disabling in October. When this is done on your email tenant, it can be anywhere from 24-48 hours where your emailing in Dynamics GP will not work.
Some of this is mentioned in these two articles:
techcommunity.microsoft.com/.../2772210
techcommunity.microsoft.com/.../2599824
Exchange Online is making these changes not on the policy level but behind the scenes, this is why it is possible to run a diagnostic against your Exchange Online and have it show basic authentication is still enabled, when it actually is not behind the scenes. This makes troubleshooting basic authentication near impossible for us right now.
These articles mention a work-around that you can potentially look into, that allows you to use a legacy endpoint to connect to Exchange Online, which still uses basic authentication, which will be valid until probably October 2022 when basic authentication is removed completely.
For Dynamics GP, we've also seen this work-around work for some customers, to use basic authentication still, while emailing via Exchange, until they can upgrade to GP 18.3 or GP 18.4 and use our new Azure AD MFA functionality. The blog mentioning this is here:
community.dynamics.com/.../emails-intermittent-failing-when-sending-out-of-dynamics-gp-not-workflow-emails
All of this being said, the recommendation is to get upgraded to a minimum of Dynamics GP 18.3.1200 and begin using our new modern authentication/MFA feature we added to Dynamics GP.
This uses modern authentication and also allows users to have MFA enabled on their user accounts, whereas MFA was not supported when emailing per Exchange in prior versions of Dynamics GP. This is mentioned in these two blogs:
docs.microsoft.com/.../multi-factor-authentication
community.dynamics.com/.../microsoft-dynamics-gp-fall-2020---multi-factor-authentication
By Oct 2022, you must be on GP 18.3.1200 or later, using modern authentication/MFA, in order to email per Exchange, otherwise MAPI would be the only other option, which requires a 32-bit email application.
Let us know if you have any questions....
Thanks