K9 app blocked by Gmail accounts when attempting OAuth 2.0 authentication

[L_C]

I tried adding a new Gmail account to my K9 mail app on Android. When I created the Gmail account, a few months ago, it prompted me to enable the Google account protection features, which I did. Unfortunately, once you do that, there is no going backwards.

When I tried to add that Gmail to my K9 mail, my phone displayed the message “This app is blocked. This app tried to access sensitive info in your Google Account. To keep your account safe, Google blocked this access.”. After I close that message, in K9 I see “OAuth sign in failed, Authorization canceled.”

I did have another Gmail account in K9 mail that was working – it was created and added years ago. However, in my attempt to get the new Gmail account added to K9, I erased my K9 mail cache and data on the phone, which caused me to have to reinstall all my email accounts (3 non-Gmail and 2 Gmail), and I could no longer get any of the Gmail accounts working.

I think the problem is with the new OAuth 2.0. If I put the password setting as Normal, it tries to connect but returns “Invalid credentials” (and I’m 100% positive I’m using the correct credentials).

Since posting this, I’ve reinstalled the latest version of K9 Mail from the Google Play store. I again tried the default Gmail settings in K9, but got the “This app is blocked…” error. So I created an app password for each Gmail account and was then able to reinstall all of my Gmail accounts in K9 using the “Normal” password authentication setting.

In the Google Help, they state that the OAuth 2.0 authentication is preferred over the app passwords. They state that they automatically block any apps that aren’t using proper OAuth access. I did try using the procedure described in this forum article…

How do I update an existing Gmail account to use OAuth 2.0?

If you used your Google password when adding a Gmail account to K-9 Mail, you need to use the new mechanism to be able to still access your messages. For this to work, make sure you’re using K-9 Mail 6.200 or newer. We tried to make the transition as easy as possible without forcing users that use app-specific passwords to switch to OAuth 2.0. The somewhat automatic way Inside K-9 Mail, manually check your Gmail account for new messages. You should see an “Authentication failed” notification…

…but it didn’t work and I had to revert back to the app password method.

Please advise.

Thank you!

[Mira]

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[kevincox]

I had this same issue on a Google Workspace that I administer. I couldn’t find any option to resolve it so I ended up enabling user/pass login and using that.

It would be nice to have this resolved, it is both more convenient to set up and more secure to use OAuth.

Not to mention the warning in the admin console saying that in the past this feature will stop working:

Starting in Summer of 2024, Google Workspace accounts will no longer support less secure apps

[kewisch]

There are some ongoing issues with Google in K-9 Mail at the moment, please see Gmail and Thunderbird for Android | Thunderbird for Android Help for more details.