Receiving email on alias but not able to send any emails - Outlook on the web?

An update: After over 6 hours on chat and the phone with 8 different Microsoft reps, I was told that Outlook.com no longer supports adding and syncing outside accounts, which is why my emails using the aliases for those accounts were winding up in the Draft folder.

This means that you can no longer send emails using aliases from third party email accounts, at least according to the support rep who finally was able to help me. This also is true for the new Microsoft Outlook app, which is modeled after the Outlook.com interface.

You can, however, still add third party email accounts to the old Microsoft app for Windows as well as to the iPad/iPhone Microsoft app. To do so with the mobile app, I had to delete all email accounts, including my Outlook email account, re-add them, then restart the app. You may have to delete all the accounts in the Windows app as well. I’m not sure since I haven’t used the app in decades and only started again when the issues with aliases occurred a few weeks ago on Outlook.com.

As I mentioned, it took me over 6 hours and 8 different reps to get answers from Microsoft about these issues. The last rep actually called me so that he could more easily help me fix things, which I greatly appreciated. I have a Microsoft 365 subscription, which allegedly comes with “premium” support. Clearly, Microsoft’s definition of “premium” and mine are extremely different.

We also have this issue now in the new Outlook. When you do a search for the alias, it just replaces it with the primary account not the alias address. This is highly frustrating. All of the new webapps Microsoft is launching are terribly buggy.

I'm having this same issue as well. Anyone?

Also having same issue.

Now end of April☹️

This is the regular option I was describing. This does not work anymore.