"can access email as usual" - have you actually tried (and succeeded) in fetching and sending new messages?

I can still send and receive emails. The message is simply a nuisance as i have to cancel it every time I open my email.

try turning off your anti virus mail scanner. My guess is it is asleep when you open Thunderbird and after the initial error is awake.

Having said that I sometimes get the issue on starting up on one of my outlook accounts. I have always assumed that both accounts trying to get mail on startup causes some sort of race condition with the outlook sever not wanting to allow two connections for different users at the same time. But for me it is like once a week.