Afrer updating /e/OS to 1.2 on FP3 I was greeted with an error notification from the Mail app about needing to fix authentication settings.
After clicking on that, I was taken to the account settings of the Mail app and when clicking Next there, accounts.google.com opened in the browser and I was greeted with:
Error 400: redirect_uri_mismatch
How do I fix this?
Regain your privacy! Adopt /e/ the unGoogled mobile OS and online services