Mac Mail 10.3 keeps crashing on Sierra
Since yesterday, my Mac Mail suddenly keeps crashing everytime I open it up.
It keeps alive for around 20-30 seconds, and then closes with the "report / reopen" dialog.
I happened suddenly and on a day where I had been using the mail for the entire day, so as far as I know I haven't done anything to set it up.
All my mails in either a Gmail or a G Suite but unless Google has done something new, I haven't changed any settings.
I'm running Mac Mail 10.3 on Sierra 10.12.6 OS X.
I can provide the Crash Report if necessary.
For the Application Specific Information in the crash report it states that
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'This method should only be called on the serialization queue'
terminating with uncaught exception of type NSException
Any suggestions or clue in to what might have caused this and how to fix it would be extremely appreciated.