I've now had this happen twice- in the panel I've set up a forward or 2 onto a long-existing DH mailbox and the mailbox has disappeared taking all of my mail with it.
I use IMAP, so there was a lot of mail. Luckily I have a fairly recent Thunderbird backup which contains the mail.
I contacted DH support and they aren't aware of anyone experiencing this before, so I thought I'd put a message here in case anyone here has. Could you let me know as I'm now worried about setting up forwards.
This has only happened since moving over to a PS, though I'm not sure that's related.