How did you determine the Deleted Folder was full?

1) I tried to delete some e-mails and received the message "Deleted folder is full - compact folder or delete some content". 2) Deleted folder was showing 64k content 3) On opening the Deleted folder I could see tens of duplicates for every e-mail OK?

What happens when you right click on 'Deleted' folder and select 'Empty Deleted'

Please confirm this is a POP mail account.

I'd prefer not to use "Empty Deleted" as occasionally I refer to e-mails I've deleted. I generally keep e-mails in Deleted for about a month before deleting. I deleted most of the multiple e-mails by using Shift and Page Down and delete. It is a POP account. Thanks

What is the size of your Trash folder?

Properties shows 4445 files and 279MB I saw that there was a Repair Folder button under Properties. I clicked it and said OK but there was no change in the number of files or the size of the folder.

I don't understand what '4445 files' means. Can you post a screenshot? http://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem

Deleted folder properties below. Number of messages, not number of files. Sorry

Is the number of messages identical to what you see in the thread pane when Trash is selected in the folder pane?

Have you tried compacting Trash (or Deleted)? Right-click the folder - Compact

Compacting is done automatically when you do an 'Empty Trash'.

Same number in Thread as in Properties of |Deleted. The Deleted folder has been compacted.

And what is the result?

It did not alter the number of copies of deleted e-mails showing.

I have now deleted all of July's multiple e-mails and I am left with:- 8 copies of each e-mail on the 1st August 4 copies of each from 2nd to 18th 2 copies of each from 18 to 28th 1 copy of each since then

Do you still get the "Deleted folder is full" error upon deleting messages?

No. Not since deleting so many e-mails on 3rd September

Good. Is there still a problem then?

My original question was "Why". I now add "Will it happen again" and "How do I stop it", but at least I now know to look for it and manually delete whn necessary. So I suppose I'll mark this as solved. Thanks for your time.