Strange comment e-mail quirk

In the past week or so, I’ve noticed that my WordPress comments had stopped being e-mailed. I use Google Mail to host my e-mail, so have my domain set up to redirect all e-mail there. If someone sends me an e-mail to me at [email protected], no problem, it goes right there. But for some reason, the e-mails from WordPress (blog comments and my backup) are going to the undeliverable folder in my domain’s e-mail account and not being directed properly at all. I use Google because I can’t get into my domain’s webmail service from work (firewall issue), but either way, I’m not sure what’s going on with the mail that only WordPress is misdirecting. I have to believe the problem lies there. Suggestions?