You need to generate an App password with Microsoft that needs to replace your usual email password in the SMTP settings in Manager. Microsoft made changes quite a while ago that requires enabling of 2-Factor authentication and creating such App password to allow SMTP to authenticate from an App such as Manager. This is not unique to Manager but to any App that uses SMTP with Outlook.
Correct and that is why you must create an app password that you will use in Manager instead of the traditional password. The username remains the same. Also ensure that 2-Factor Authentication is enabled in Microsoft.
In another accounting program, I also have an outlook.com address from which mails were pulled in before, but now, after September 16th no more.
Not even with that app password if the program is not supporting this new OAuth2 method
Whatever you report here I have no problem but there are 2 actions I needed to take:
Enable 2-factor authentication with Microsoft
Create the App password and use that form SMTP in Manager
I reported earlier that for some reason Manager seems to persist keeping the old password which I also reported to @lubos because I cleared the cache. etc. I resolved it by opening a vanilla browser, deleted the existing credentials saved it and then created a new entry.
For Desktop version that may even be more complicated and I did not try.,
For some reason since not too long ago Manager seems to keep the old password in the database rather than allowing us to delete it. I reported this to @Lubos but so far no improvement. I am tempted to see this as a bug but there are now several users reporting this and it should be fixed. maybe the HTTP solution is now preferred but I also already commented that for some that may be ok but if you want to be sure that your email is delivered it is not. From my perspective in Accounting I want to be sure that Invoices get delivered and therefore did not adopt HTTP whioh is nice for webforms and similar but not for reliable accounting.