Some view options may cause messages to not appear, e.g. the Quick Filter and some options under View > Threads:

https://support.mozilla.org/kb/quick-filter-toolbar https://support.mozilla.org/kb/ignore-threads

What you say here would seem to indicate the problem is something else, though:

I repaired the inbox and it is now showing several mails that I deleted in the last few days (by emptying the delete folder having previously deleted them).

As strange as it may sound, deleting a message from a folder doesn't really cause it to be removed from there. The message is merely marked as deleted and remains there until the folder is compacted. What you delete when you empty the Bin/Trash is a copy of the message that Thunderbird placed there when you told it to delete the original message, but the original message remains where it was, just marked as deleted.

Even if it remains there, repairing the folder shouldn't make a deleted message reappear, though. If it was marked as deleted, it should remain hidden, and the fact that some deleted messages reappear would seem to indicate there is a problem with the file where the folder contents are stored on disk.

Do you keep a lot of mail stored in Inbox? What type of mail account is this (POP, IMAP)?

Hi DavidGG

Thank you for such a speedy response and the useful info about deletions. To answer your queries, I keep very little in the inbox and use POP. And just in case it's relevant, I close down TB every night and copy the full folder the next morning before opening again; nothing appeared untoward in any of that.

However since logging this one of the webmails from which I download to TB has stopped receiving mail, though it can still send. It's probably totally unconnected, but... I'm chasing it.

Mrs F