IMAP (Internet Message Access Protocol is an email protocol where your messages are stored on the ISP's server and not on any given computer. The advantage is whether I am in an internet cafe, on my iMac at home, on my MacBook Air on the road, or using my iPhone I have all of my messages available to me and if I delete a message on any one of the various machines, it is deleted on all of them.
From reading the Starband web page, I do not believe they support IMAP. AFIK most ISPs do not. If you are interested in IMAP there is a way you can get it through Google's GMail but still using your Starband address. If you are interested let us know and someone can walk you through setting that up.