If your PC's are running Windows 95, it supports multiple protocols, and you can setup a TCP stack to run along side the IPX stack. Then you need a properly configured POP/SMTP e-mail client like Eudora for example.
You can connect different platforms together using Ethernet. The Macintosh and PC computers will not see each other because they are running different protocols, but with software like AppleShare Client for Windows by Apple Computer, Personal MacLan Connect by Miramar Software, or COPS Talk by COPS Inc. will let PC and Macintosh computers share files.
The Tech Info Library article titled "Locating Vendor Information" can help you search for a particular vendor's address and phone number.