Xerox has a utility to do just what you ask but only works on Xerox printers. My Phaser 8200 has an email server built in and will accept emailed documents directly to it.
I thought Lexmark might have something similar if your model supported it but after reading the Lexmark website, I don't think it will.
So, we must find another way. Give us a little more detail such as SME version, is it your file, web, mail server or just a gateway? Is the printer hooked up to the SME server or one of the clients? Dial-up, cable, dsl? etc.
Give as much detail on both ends (main office and remote office). With the correct setup, it might be easier to just use a VPN. Let's see what you have.
Good Luck,
Paul