To solve a problem with spam on our server we tried to forward e-mail from our dedicated server's mailserver(matrix smtp service) to gmail, but while most e-mails got through e-mail from our own domain all went missing. They weren't in the inbox or spam or anywhere else. We've had to go back to using the old system, which means my boss gets a huge amount of spam.

We have a windows 2003 server with iis 6 and the matrix smtp service installed. I've toyed with the idea of installing a mail proxy like ASSP but it looks pretty complicated. We're hosting 20 domains on the server as well as our own which has an online shop whose payment system depends on email. I can't start playing around with complicated solutions when it could have disastrous consequences and I don't know enough to implement them safely.

So my question has two parts: Part One: Why can't we forward e-mails from people using the same domain. If our domain was foobar.com then [email protected] can't receive from [email protected], but he can receive from everyone else.

Part Two: Is there a really simple server side solution to spam that would work with matrix? For instance popfile?