Forward to helpdesk feature

[artcz]

It should be possible to fwd email received on a private account to helpdesk and then continue discussion from there.

Currently I think this would be technically possible, but unpleasant, because it will mark whomever did the FWD as submitter, and will require manual action to update that to an email address of the person who sent the email in the first place, so that sending email would still work correctly.