Agreed. At [old job] we saw a lot of user-entered e-mail addresses that were "correct" (according to so-called validators) but wrong, like "www.screenname@aol.c

Agreed. At [old job] we saw a lot of user-entered e-mail addresses that were "correct" (according to so-called validators) but wrong, like "www.screenname@aol.com" or "example@yahoo".