[Android Q&A, Help & Troubleshooting] GalaxyA325G:
Update on 3rd-party MUAs (e.g., K-9 Mail) using OAuth2 on Android after May30th, 2022... which we have been searching for since early March of this year when Google notified us of the demise of the venerable login/password credentials.

PSA: K-9 Mail is (AFAIK) the ONLY 3rd-party MUA on Android working after May 30th, 2022 by using OAuth2 over the web (and not andOTP/FreeOTP or app passwords, etc., all of which require 2FA/2SV/MFA/MSV which results in a loss of privacy!)​

1. I am a typical Android user who was badly affected on May 30th 2022, when Google unilaterally stopped supporting login/password authentication for 3rd party Android mail user agents (MUAs).

2. Since then, I've been desperately looking for a 3rd-party MUA which can log into a Google account WITHOUT 2FA/2SV/MFA/MSV and without creating a mothership tracking account on the phone.

3. Google (seemingly) allows MANY ways to authenticate a MUA onto the Google email servers; but all but one method (AFAIK) requires a "second something" (which is often referred to as 2FA/2SV/MFA/MSV) - which trades privacy for security.

4. The one method of authentication that doesn't require 2FA/2SV/MFA/MSV is OAUth2 (which itself is inherently insecure, but the problems with OAUth2 are not the point of this thread).

5. I have a Google email account, like many others... simply because it's the best free email account that I can find.

6. However, I am one of those Android users who cares a lot about privacy (where privacy is a thousand things, much like health and hygiene is a thousand little things - where people who care about privacy never just give up - just like people who care about hygiene never just give up - but they understand that many others do just give up, and that's OK.

7. One of those privacy little things is I don't have a Google Mothership Tracking Account on my unrooted Android phones, and I never will.

8. Hence, I could never use the Android Google GMail app to log into my Google email account because it CREATES that mothership tracking account.

9. Another of those privacy little things is I don't use 2FA (aka 2SV/MSV/MFA, etc.) which trades privacy for security since a "second something" is always needed in your hands (e.g., freeOTP, andOTP, etc.).

10. Some MUAs (such as Thunderbird on the PC) use OAuth2 over the web, but until this week (AFAIK), there were ZERO 3rd-party MUAs on Android which authorized Google email using OAuth2 over the web (mainly because Google apparently requires an annual security audit costing thousands of dollars for anyone who does).

11. Therefore, AFAIK, every third-party MUA stopped working with login/password on May 30th, 2022, where some of them (e.g., Fair Mail) were forced to switch to some other authentication mechanism, one of which was to authorize via OAuth2 using a Google Mothership Tracking Account (which the app would CREATE for you, whether you wanted it to do so or not). Just like the GMail app does.

12. Apparently, as of this week, the developers of K-9 Mail (teamed up with the resources of Thunderbird), are the first free 3rd-party MUAs on Android that allow OAUth2 authentication over the web with Google email accounts.

13. Last week OAuth2 was added to K-9 Mail for the first time (version 6.200), but it CREATED a Google Mothership Tracking Account in order to authenticate with the Google email servers.

14. This week, I was advised that the K-9 Mail version 6.201 was updated to perform that all important OAuth2 over the web. I tested it just now. It works. Note the K-9 team probably have resources that most Android developers lack now that they've teamed up with the Mozilla Thunderbird folks.

15. This is a PSA, and, a question of whether you know of any other 3rd-party Android MUA which can authorize OAUth2 with Google email servers over the web (WITHOUT creating a Google Mothership Tracking Account on Android).

Disclaimer: I am just a user; I am NOT affiliated in any way with anything.

Spoiler content hidden.

In summary, as far as I know, K-9 Mail is the ONLY 3rd-party Android MUA that can connect to Google mail servers after May 30th, 2022 without 2FA/2SV.