SendMail relay open if 'from' and 'to' match domain
 

I'm using Fedora Core 1, with SendMail 8.12.10.

The relay is closed, except for the company's internal network, which is 10.0.0.0/24.

But there's one flaw: if I connect to the Internet from home, and I send a message using the company's sendmail as relay, from user1@mydomain.com to user2@mydomain.com, the server accepts it.

So my users are receiving loads of spam from spammers who identify themselves as userx@mydomain.com, and worse, using our own server as relay.

I thought that this would only happen if I configured sendmail with:

FEATURE(relay_local_from)

but this is not the case.

Does anyone know how to solve this?

Thanks,

Carlos