Networking Protocols: Telnet, SMPT, POP3 & IMAP

Telnet, SMTP, POP3, & IMAP Telnet is a “remote terminal connection” protocol that connects a computing system to a remote source.  Telnet runs on port 23, it’s also unsecure and is both a TCP ad UDP protocol, and has generally been replaced with SSH. This type of transaction is totally transparent, any data is visible and unsecure which is not desired.  It’s used with both TCP and UDP. Our next group of protocols deals with email transmissions over the network, they are SMTP, POP3, & IMAP and these are all TCP protocols. SMTP stands for Simple Mail Transfer Protocol and runs over port 25, runs generally between a dedicate server (think Exchange or mail server) and a computer or other device with email client software as the interface such as Outlook ad even internet based email such as Yahoo, Gmail. POP3 uses port 110, its stands for Post Office Protocol 3.  POP3 is a protocol that downloads email from the server for email transactions, it’s not a send/receive protocol, it only provides download services to the client computer.  It must be configured to retain emails on the server after download to the client else it deletes them by default. IMAP uses port 143, it’s a networking protocol for email.  You have server to download to the client and retention of the email and far more robust than is POP3. For each of these protocols, we map out the entire transaction process to demonstrate how emails are sent, whether or secured, transmitted, and then what happens when they are received on the other end (server + client).
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