A user has complained about a problem with Thunderbird for a long time. The problem is that sometimes when the user sends a message, the message got sent but then a pop up window shows up saying “Error Copying to Sent Folder”. I thought it’s related to the mail server and did not pay close attention to it.
I did a google search on this problem yesterday and found this page. It looked promising, so I tried it on my user’s machine. The user has yet to encounter this problem after the changes. Here are the steps for Thunderbird 126.96.36.199.