How E-mail is Sent
After you compose an e-mail message and click send, your message is sent as a stream of packets using the Internets TCP/IP protocol. (TCP stands for Transmission Control Protocol/Internet Protocol. They are the communications protocols that underlie the Internet.) Each packet contains the address of the destination and of the sender, as well as much more information.
Routers on the Internet look at the addresses in each packet, and send the packets on the most efficient path to their destination. Factors that affect the packets’ routes include things such as traffic volume. Each packet may take a different route, meaning the mail packets can arrive at the destination out of order. When all of the packets arrive at the receiving address, they are combined into an e-mail address the recipient can read.
You can send the same message to several people by using a mailing list. Mail is routed to everyone on the mailing list by a “mail reflector.”