Thanks everyone, for all of the help. I use my ISP as my mail server, not Hotmail, or anything like that...and I don't use Outlook Express or anything like that, AND I check my e-mail several times a day so I shouldn't be exceeding my limit. Therefore, I feel fairly safe in calling my ISP and talking to them about it, because it's not any of the reasons any of you posted that it could be my fault. So, once again, thanks to everyone for adding each of your pieces to the puzzle! This is what's nice about belonging to a community like AntiOnline.
I really appreciate it!