E-MailRelay is a simple SMTP proxy and relay MTA, written in C++, for Linux and Windows. As a proxy all messages can be passed through a user-defined program, such as a spam-filter, which can drop, readdress, or edit messages as they pass through.
This is an amazing piece of software. Layered atop (or alongside) a SMTP MTA, emailrelay provides an elegant yet simple solution for mobile access to email services. The software appears to have been developed with thoughtful consideration of security features and resource demands. It's light weight and quite flexible in deployment options. I've searched for something like this for years ... now, my search is over.
nice proxy- very useful!