I have been happily using Kontact (which in turn seems to use KMail) to connect to my GMail account via IMAP, until recently.

I had to fight to get Kontact working after a disto upgrade*, and as part of my troubleshooting efforts I removed my GMail IMAP accounts from Kontact. I think I've got the original Kontact problem sorted, but now I can't re-add my GMail accounts. When I trying to do so, an oauth (I think?) sequence kicks off from Google and prompts me for which Google account I want to use, and prompts me for my password. After putting my password into this oauth prompt, I get the following message:

Sign in with Google temporarily disabled for this app
This app has not been verified yet by Google in order to use Google Sign In.


I've googled around for other kontact users suffering from the same problem but come up empty. I have found search results for that message in general (not referencing Kontact), which says that the author of the application has to verify it with Google... I'm not sure if I need to fill out a bug report with my distro and/or the Kontact project; or if maybe there's some kind of oauth-related cookie on my system that I fudged up during my many attempts to get things working; or if tripped some kind of attempt limit in Google. Any advice?


*Upgrading to Debian Buster from Debian Stretch caused Kontact to reliably hard freeze my box. I found that akonadi was also producing errors. The ultimate cause seems to have been akonadi being configured to use MySQL, Debian dropping MySQL in favor of MariahDB in Debian Buster, and my upgrade somehow resulting in MySQL being uninstalled but without getting MariahDB installed in its place. Installing MariahDB has fixed akonadi and the freeze issue.


P.S.: I tried setting up Evolution to see if it would have better luck. I was able to set up my GMail IMAP accounts with no problem, which makes me think it wasn't some kind of attempt limit in Google unless such a limit was somehow smart enough to differentiate between the two programs.

I was able to connect to the GMail IMAP by manually modifying the account settings in Kontact/KMail. Changing the Authentication method to "PLAIN" did the trick! It had been set to "Gmail".

I didn't have to modify any of the other settings from how Kontact/KMail's (Akonadi's?) new account wizard had, but I'll include them here in case they help someone. Replace the stuff between angle brackets, of course.

(Under Kontact/KMail's "General" tab)
IMAP Server: imap.gmail.com
Username: <yourfullusername@gmail.com>
Password: <your gmail password>

(Under Kontact/Kmail's "Advanced" tab)
Encryption: SSL/TLS
Port: 993
Authentication: PLAIN