|MadSci Network: Computer Science|
There are no name translation tables for individual e-mail addresses. For example, you have your e-mail forwarded to a different account, but someone else on your ISP may not. DNS routing tables only work for the domain name itself: for instance, my ISP is stargate.net. That translates to 220.127.116.11. If I had mail forwarding services, the sender would send mail to the address I specify. The forwarder sees that the e-mail came to your address and isn't supposed to stay there, and so it then shuttles the e-mail to your real address.
Try the links in the MadSci Library for more information on Computer Science.