How do you stop thunderbird from syncing a specific mailserver (imap)?

As pointed out by Psychogeek the only solution I found was copying to a local folder and deleting the mailbox.

I had an unusual issue with a mailbox that I no longer had access to (a pop-up opened every time I clicked on one of the folders within it asking me to check my password/say it couldn't connect), as I could not copy the messages from within the mailbox (not sure why). This was circumvented with the copy-folder add-on which worked fine.

P.S. I have no idea what was causing the problem.

It's too bad that there's no built in option for this, but I managed to find the following dirty solution which is good enough for me:

1. Change the server name to 0.0.0.0. This way Thunderbird won't be able to connect to the server. I get no password prompts. I do see a message at the status bar that says that it's trying to connect to 0.0.0.0. Not perfect, but that's the best solution I could find.
2. Uncheck automatic new message checks on startup and every 10 minutes. Saves the automatic connection attempts.