Same here, observed since we moved from 60.8 to 60.9.

It doesn't happen to everybody, but some have a full mailbox download, several times a day.

It often happens simultaneously with a message saying "there was a connexion failure with the account provider" asking if we want to "retry, change password or cancel".

We also observed connexion attempt to mail account provider of mailbox that has been destroyed for a while. God: Mail Account Zombies ?

Maybe it's 3 different troubles. Looks like profiles corruption, why?

I didn't try to go back to 60.8 because we are on a shared windows terminal server and the one who is responsible for upgrading is the first who launch Thunderbird in the morning.

who is your provider?

OVH (France)

But Thunderbird also tell me it doesn't manage to connect sbs2003 that was an internal server, down for 3 years now.

No email account shows any link to this server for this profile, but there was one in the past.

Why does it try to connect to this server now?