I've had more than one of my contacts' email account get hijacked by Boxbe. I don't know much about this system, but the message goes like this:
Please add yourself to my Guest List so your messages will be delivered to my Inbox. Use the link below.
I've never added myself to anyone's guest list, and I never will. I'm afraid adding myself to a guest list will result in my email address being taken over by Boxbe and my contacts getting these annoying messages.
I could be wrong--maybe it doesn't work like this. But all of my friends have been surprised when I tell them my email got blocked. Seems they didn't intend to put this virtual roadblock on their email address.