A day after Apple released macOS 10.14.4, many users reported an annoying bug related to authenticating Gmail accounts via Apple Mail.
The complaints on the Apple Support Forums claim that macOS 10.14.4 breaks the process of authenticating a Gmail account. More precisely, when attempting to log-in to their Google accounts, users are put through endless loops, bouncing between macOS and Google’s sign-in page in Safari.
Considering users’ comments, it seems that the sign-in problems relate strictly to the Apple Mail application. Currently, no other apps relying on Google information are affected by this problem.
While trying to solve the issue, some users have removed and re-added their Google accounts, disabled two-step, changed passwords, etc. However, none of these actions solved the problem.
At the same time, the issue doesn’t seem to be unique to adding new accounts to Mail on macOS as it affects existing accounts as well.
When rebooting from installing the update, users are being prompted to authenticate their Google account again, which places them in the above-mentioned endless loop.
Other users have had problems with adding new Google accounts to the Mail app on iOS 12.2, while macOS might return sign-in credentials as failed. At this point, this issue seems to affect only Google Apps accounts.
Currently, there is no information if the recent authentication bug affects every user who runs macOS 10.14.4, or a subset only. However, if you use Google accounts in Apple Mail, it might be better to put off the update to macOS 10.14.4 until Apple addresses the authentication issues.