Okay. I logged in and purchased a virtual mail box and figured out a couple things, but I didn't find a link to the help center until I found the FAQ link on the dedicated and virtual pages. Conceptually, this sounds very ambitious and unique, although I haven't looked into this niche market at all. Clearly it is an original idea, and at first I thought it was all about email. Try to convey through pictures (mailbox, packing tape, something like that) what you are doing -- that this is NOT about another free email service, but it is about a connection to your physical mail from anywhere in the world. That is a great idea, but I think people won't get that at first. Secondly, I would embed a lot more explanation into your control panel pages -- I still am not clear on the difference between virtual and dedicated, for instance -- put that directly on the page I'm on. You may also consider stepping a user through a wizard after they register to ensure that all the right things are created for their account, without requiring that they first educate themselves on the site layout.
All told, however, I think there is a lot of promise here. Very original.