I would imagine that your email provider set them up on the server and Thunderbird is simply showing you what is on the server.

Are these in addition to folders whose names you do recognise, or in place of?

They are in addition to the familiar folders in the pop version from the same provider.

I suggest you ask the operator of the IMAP server in question.

Thanks for your reply. I have contacted my email provider (Time Warner) but they never responded.

I think most of the names are explanatory. Given that TWC have offered SMS /Email gateways for years, I would assume some of the folders are for SMS messages while others are for mail. But which is which I have no idea.

I am only guessing, but it may be TWC uses Microsoft Exchange as their mail system as that has a notes folder.

Thanks for your reply, Matt. I don't think that most folder names are explanatory; for example, what is the distinction between the Sent, SentMail and Sent Items folders, and the Deleted Items and Deleted Messages folders? I can't get a rational explanation from TWC on this matter.

Thunderbird has a set of standard folders which it will generate for any account you set up. These include Inbox, Sent, Trash, Drafts and maybe Junk.

Anything else which magically appears is your email provider's idea of what you need. These are folders twc create when they set up the account.

So long as Thunderbird is doing all the work, you can use its folders and ignore those generated by twc. However if you try to delete folders set up by twc, they may well be automatically regenerated. If twc assume responsibility for making copies of sent messages then these copies may well be put into Sent Items or Sent Messages. Since twc invented these names, only they know for sure what is the intended use of each folder. As Matt commented, "messages" may be a reference to SMS (text) messages.

If you find that the twc folders can't be disabled or done away with, the pragmatic thing is just to roll with it and use them. Most of these functions allow you to set, in Thunderbird, which folder it should use. So you can select Sent Items or whatever if that's the one that works most smoothly.

I think you're making a big issue out if it, unnecessarily. I'd just use the account and see what goes where. You may find that some folders remain empty. Maybe they can be deleted. If you find some messages, say sent messages, end up in two different locations then you have to work out what you can actually change. Whilst Thunderbird is flexible you'll probably find that twc are not, so in this case it would be easier to tweak Thunderbird to use the twc folder. In the case of sent messages, you may find that whatever you do, twc make a copy in a Sent Messages or Sent Items folder, so you may as well just switch off this saving function in Thunderbird.