Yes, thank you, I've done this, but it's going to deplete my storage space in Gmail before long. It's obviously a Lion-related issue, since I've never experienced this before (and I installed Lion this morning). I appreciate your help.
No, how this site sends e-mail notifications is not in any way related to the system you're running. Why it just started, I don't know, but it's not related to Lion unless I'm misunderstanding what's going on.