You aren't composing the mail correctly (no From: header, no blank line between headers and body) and your ISP is adding one. As other people have said, please read the FAQ on this, because web->mail scripts have been a favourite source of errors for over a decade.

If you've ever run a web server and looked at the error logs, you'll see there are spammers still trying to find formmail.pl exploits from eons ago.

Your program in its current form might not be exploitable (hard to tell - since I don't know where you get $name from - if it's from the form can I enter ';rm -rf /' or similar and have some fun?) but things get extended over time and you may end up providing a spammer's gateway (or an exploitable hole on your ISP's webserver).

You might also want to look into taint checking if you haven't already. Have fun.