How do I activate iMessage without the use of my phone number or SMS service?

I am currently abroad in Italy for an extended period of time (my home is the United States) and my cellular plan is currently suspended (seeing as I have no use for a Verizon plan in Europe). However, I have been told that I have to use my phone number to activate my newly downloaded iMessage. Is this the only way to activate it or could I potentially do it through my Apple ID or e-mail?