My sent emails were saving just fine to the "Sent" folder in Thunderbird until two days ago, but now suddenly started hanging indefinitely on "Copying Message to Sent Folder." The emails themselves appear to be sending just fine, so this is a problem only with saving to the Sent folder. I find it very useful to have copies of Sent emails, so I would prefer to fix this rather than just turn off the option.

I did google around a little bit and found several simple fixes for the problem (change security connection, choose "Other" in folders & copies, etc.), but none of them worked for me. Any help would be greatly appreciated!