Nothing like that Doug - at least with respect to any third-party app. It may very well be my mail app, but it only keeps settings and other pieces of data in one place that I know of. And I've gone through with a fine-toothed comb to remove any references to these folders that keep getting recreated.

And I don't even know for sure it's the mail client. I do know at this point it's not either of the mail clients for iOS, since I deleted Sparrow and deleted all my mail settings from the default client. The iPhone no longer knows about any email servers at all, let alone accounts or folders.

I can really only think of one next step and that's the nuclear option. Back up all my mail by export (not copying the folders from disk), and then nuke everything to do with Mail on the Mac. Then import what I exported and set up the accounts manually. Ugh.

Apart from the pain in the ass it is to do this, I still don't know if it will work, because the issue may very well be on the server. Though the support staff has not been able to tell me that and all they've done is repeatedly deleted the folders on their end.