Outlook Android app cannot login IMAP email server.

I fully concur with your assessment.

On numerous occasions when I have pointed out the errors, I was immediately informed that it was not Outlook app, but my ISP. Also on every occasion I had to listen to a lesson of how to input new account details.

After I analysed this issue to its bitter end, it is obvious that the App is faulty. No supporter can argument around that, especially since the App has been updated to allow the selection of the TLS/STLS types.

Clearly, this is not an ISP, not MSP nor account issue.

The Outlook App for Android is buggy and we can even say, what exactly is buggy. So, where is the product owner to take this issue now?

I fully concur with your assessment.

On numerous occasions when I have pointed out the errors, I was immediately informed that it was not Outlook app, but my ISP. Also on every occasion I had to listen to a lesson of how to input new account details.

Don't know if that helps you on this topic, but I had the same issue and was trying out absurd scenarios just to find out that STARTTLS for IMAP in Outlook App is not working at all.

Direct TLS via 993 works fine.

The joke is that STARTTLS for submission/smtp works fine. That's really absurd, but I gave up trying it with 143 using this app, since 993 seems to be more widely adopted by many MSPs anyway and some even disabled the use of 143/IMAP. Check your MSPs DNS SRV records for _imap and _imaps.

I'm not sure which RFC Microsoft thinks it is following here, but STARTTLS was supposed to replace direct TLS as far as I understood in the past. After the IETF has completely deprecated any plaintext authentication, the recommendation was to use implicit TLS. Seems like Microsoft changed its path.

RFC 8314 seems to recommend implicit TLS throughout any communication between the MUA and MSP, with the exception that _submission was adopted due to port configuration on existing MSPs using port 25. For an MTA it is understandable, because some vendors transferring mails dont know (except when using DANE or MTA/STS) if the other side supports TLS at all. That's why there is a choice to use plain mail transfer or STARTTLS-upgrade the transfer. Some MSPs used 25 for MUAs, growing numbers use 587 today.

Coming back to above mentioned lines, for IMAP, with RFC8314, deprecation of plaintext and the recommendation to use implicit TLS, it makes sense to disable STARTTLS.

Unfortunately Microsoft didnt let the users any choice to amend this. This may go along with the 2019' approval of the Outlook App to be used by the Pentagon Department of Defense.

That's why, in my opinion, Microsoft does not consider this a bug and does not respond to "bug requests".

What you can do is to try entering your MSPs connection details manually, i.e. smtp-host, user,pass, but IMAP with Port 993 and SMTP with Port 587. This may then work as it did for me.

My Samsung app is working fine, I use Outlook for work (365)
I think Microsoft are genuinely embarrassed to the level of not admitting to this issue, obviously not tested in QA. I suspect a silent update in a few days.

The worst part is you wake in the morning thinking someone has hacked your email and changed the password.

Welcome to the club.

Mine is almost 2 years in the making and still no solution on the horizon.

I now use BlueMail without a glitch.