What are the possible endings for a web address (eg Yahoo,AOL,Hotmail...)?

I have patrickman21 (has been altered for security reasons) but I don't have the @ such and such part. So what are all the possibilities (eg yahoo,aol,hotmail). I have tried yahoo, aol, and hotmail already so what are all the other possibilities out there?
What are the possible endings for a web address (eg Yahoo,AOL,Hotmail...)?
Try GMAIL, YMAIL, ROCKETMAIL, REDIFFMAIL, MSN and Sifymail.