using mail() for multiple email address...

Hello all, I have a strange problem with the mail() function. It may not be php at all. I have multiple email accounts at my website. I just started testing the mail() function to learn how it works. When I send to multiple address' separating them via a comma, all goes well until I send the same email to my main account and another address that in turn redirects it to my main account. For example: if (mail("main@domain.com, redirectedtomain@domain.com", "test", "no body really...")) print("successful"); else print("unsuccessful"); Normally, the two emails would end up in the same pop account but don't seem to be when I use the above script. If I send to one or the other they receive appropriately, but if I send to both at the same time, I only receive one email, not both. If anyone can help me as to why this is and if there is a remedy, I'd sure like to know about it. Thanks a lot!! -Adam Reiswig