I'm surprised that you received no error messages about this.

There is no error message at all. the function hangs up and just keeps spinning.

It's possible your Firewall is blocking access, so check this: Exit Thunderbird Access Firewall Make sure Thunderbird program is set up as an allowed program.

Also check this: Are you receiving emails onto the server - access webmail account via a browser to check it.

If you have used up your server quota then server cannot receive emails. This means Thunderbird cannot download because there is nothing to download and you cannot send because server cannot receive new mail. You would need to create space on server by deleteing a load of old emails or get copies of received old emails into Local Folders account before deleting them from the imap account.