Email Service Protocols

 

 SMTP

 SMTP stands for Simple Mail Transfer Protocol. SMTP is used when Email is delivered from an Email client, such as
Outlook Express, to an Email server or when Email is delivered from one Email server to another. SMTP uses port
25.

 POP3

POP3 stands for Post Office Protocol. POP3 allows an Email client to download an Email from an Email server. The
POP3 protocol is simple and does not offer many features except for download. Its design assumes that the Email
client downloads all available Email from the server, deletes them from the server and then disconnects. POP3
normally uses port 110.

IMAP

IMAP stands for Internet Message Access Protocol. IMAP shares many similar features with POP3. It, too, is a
protocol that an Email client can use to download Email from an Email  server. However, IMAP includes many
more features than POP3. The IMAP protocol is designed to let users keep their Email on the server. IMAP
requires more disk space on the server and more CPU resources than POP3, as all Emails are stored on the server.
IMAP normally uses port 143.