Email protocols

Email protocols

1. Simple Mail Transfer Protocol (SMTP): Used to send an email from clients to servers, and for transferring email between servers. It never is used by clients to receive an email from servers.

   • SMTP typically uses TCP port 25.

2. Post Office Protocol (POP): Used by clients to receive email from servers; never used to send an email.

   • Currently at version 3, or POP3. POP3 works best for accounts accessed only on one device, and uses TCP port 110.

3. Internet Message Access Protocol (IMAP): Used by clients to receive email from servers; never used to send an email.

   • Currently at version 4, or IMAP4. IMAP supports more features than POP. It works better for accounts accessed from multiple devices, but it also requires more server resources.

4. Messaging Application Programming Interface (MAPI): A proprietary protocol used by Microsoft Exchange email servers. It both sends and receives email, and has other specific features used by Exchange.

   • It's not usually used on the Internet, but is popular in Microsoft-based networks and email clients.

5. By default, SMTP, POP, and IMAP are unsecured, but each can be used with the same SSL or TLS protocols used by HTTP. Depending on your email server configuration, secured access might use different ports.