How does email know where to go?
When you type an email address for a message and press send, how does the email know where to go?
Your email client (email software) wraps your email along with some information about the message and sends the email to your SMTP server (SMTP server handles outgoing email. SMTP stands for Simple Mail Transfer Protocol) The SMTP server you use is configured in your email software. Most people use the SMTP server provided by their Internet Service Provider (ISP). Or if you use web-based email such as Hotmail or Yahoo Mail, you have no control over the SMTP server as it is built in.
Your SMTP server accepts the email, looks up the IP address of the destination server, breaks the message into packets, and sends the packets to the destination through a series of “hops” (usually a sequence of very high-powered routers). The route your email takes across the Internet is determined by different routers. Routers used for Internet routing have been compared to supercomputers. They look at various possible paths to the destination and decide the best route to take. Individual packets may all use the same route, or some may go through one route, then the router may decide that there is too much traffic along that route and send the rest of the packets through another route, or a variety of routes. other routes. .
Once all the packets have been received, the destination server (usually a “POP” server) puts the packets back together and puts the email in a special file and waits for the recipient to request their email.
Email servers have a real conversation. As you can see below, they are even very polite. This is a real conversation with the identification information obfuscated. The sending server connects to the destination server. He says hello. The destination server responds with ELHO. They are even on a first name basis. The sending server says, “I have a message for one of yours, and it’s this big.”
The destination server looks up the email address and checks if it wants and can receive email for the recipient. Then it tells the sending server. “Okay, Send It”
The sending server then says, Ok, I’m sending the message. You’ll know when it’s done when you see two carriage return line feeds (CRLFs) next to each other. The receiving server then acknowledges receipt of the message and ends the conversation.
Connection to xx.bxxx.bixxd.com [61.00.00.122]:25 … connected
SMTP (receive) 220 nxx01p.mx.bixxd.com ESMTP server ready Tue, Dec 23, 2008 21:58:40 +0000
SMTP (send) EHLO um-232.shxxs.net
SMTP (reception) 250-nxx01p.mx.bixxd.com 250-ETRN 250-AUTH=LOGIN PLANO 250-AUTH LOGIN PLANO 250-PIPELINING 250-DSN 250-8BITMIME 250 SIZE 15728640
SMTP (send) MAIL FROM: 411.4.600062-12189942 @ Selxxxization.com (send) RCPT TO: kxxxy @ bixxd.net
SMTP DATA (sending)
SMTP (reception) 250 Sender 411.4.600062-12189942 @ Selxxxization.com and extensions (OK
SMTP (receive) 250 Recipient kxxxy @ bixxd.net OK
SMTP (receive) 354 OK Send data ending in CRLF.CRLF
SMTP (send) writing message and ending . . . . . . .
SMTP (receiving) 250 Message received: [email protected]
SMTP (send) EXIT
