There is no 'sent' folder showing for the account

Is this a POP3 account or IMAP?

If IMAP, is the folder visible when you use the provider's webmail page to view the account?

If IMAP, right-click on the account name in the Folders List and choose "Subscribe:" Click the Refresh button and make sure the folder is listed and has a check mark by its name.

Check the setting <Account Settings | (the account in question) | Copies & Folders | When sending messages, automatically [x] Place a copy in> and make sure that's set to the proper folder.

Thanks, it's IMAP I have the same accounts on my android versions of Mozilla with all the same settings and each one shows the folders one would expect to see. I've been banging away at this problem all evening so I'll check out your suggestions tomorrow when my brain has settled!

OK. Don't spend too much time comparing the Android and Desktop versions of Thunderbird. Despite the names, they don't have much in common.

Thanks - I've just opened up Mozilla on my laptop and it seems to have sorted itself out!