Outlook 2016 doesn't accept password or app password

So, I use Office 2016, and of course Outlook 2016, which is not compatible with the new authorization rules. I have been struggling with this entire depreciation of older Outlook versions for a few months until Microsoft finally let us know what was happening.

I downloaded the "Outlook for Windows" App. It is eligible for the new authentication rules, and is free from the Microsoft store. It is certainly different, and does not seem to have all the features of Outlook 2016.

However, once I downloaded the "Outlook for Windows" app, and set up my outlook.com email in it, then the Outlook 2016 install settled right down. I am running both at the same time. My original thought is I would take some time to learn the new "Outlook for Windows" app, while still using my more familiar Outlook 2016 app.

So, to my surprise, so far at least, there have been no disconnects from authorization for my Outlook 2016 since installing and setting up the "Outlook for Windows" app. Not sure what is going on, but as the "Outlook for Windows" app authenticates my outlook.com email, the Outlook 2016 app flies under the radar. Maybe.

Anyway, I am letting the "Outlook for Windows" app just run in the background, and I am still happily using my Outlook 2016 app with no disconnects from authentication. For now, at least.

I tried using Outlook 2021 to access my POP3 Outlook accounts and can confirm that it didn't fix the intermittent login issues.

I've decided to use Thunderbird, which works fine and looks a lot better than Outlook 2021 in my opinion. It was a bit of a faff migrating all my emails across (had to use an earlier version of TB for the conversion from the PST file and then upgrade to the latest version of TB) but I think it has been worth it.

With the way Microsoft seem to going I expect I will eventually have to move from Windows as well!

I have posted about similar experience a while ago. I added my Hotmail account to my work Office 365's desktop Outlook (not pop3). I was having the same auth issue. While some of the MS people on these forums try to be helpful, I generally don't believe 100% what they are saying My experience has proven they are not right in many cases especially now that Microsoft is making a lot of changes to all of their products.

I'm confused.

Why would you want to use an Outlook account as a POP3?

Office 2021 (Outlook 2021) supports modern authentication when configured as "Outlook.com/Exchange"

So why would you want to use POP3?

This is an interesting (apparent) solution.

Is it still working for you?

Does the free Outlook app support multiple accounts?