Thunderbird is not saving sent messages

hello
try right-clicking on the Sent folder, properties -> repair the folder

There's an easier way. Create a folder called "Sent," go to settings<copies and folders, then check the box for another folder and choose: your email address<incoming mail, and select the Sent folder you created.

Hello,
For my part, it’s not working; I have two addresses address@ovh, for one there’s no issue, but for the other, even though the same settings are applied, I get the error message “Mailbox doesn't exist” (and the messages don’t even send) and the repair indicates the same thing...
However, if I specify a different destination folder, it works, but I would like to know what’s wrong so that it only doesn’t work on one of the two email addresses?
Any other thoughts?
Thanks :)

Please specify your account settings (especially whether it is POP or IMAP, and what your email service provider is).