Email Servers

An email server is a mail transfer agent (MTA) used to route email and act as a mail server by storing email and supporting client access through the use of protocols, such as Post Office Protocol and Internet Message Access Protocol.

There are three types of email servers, these are Post Office Protocol 3 (POP3) servers, Internet Message Access Protocol (IMAP) servers and Simple Mail Transfer Protocol (SMTP) servers.

POP3 servers are commonly used by most email services and Internet service providers, particularly for personal email accounts. POP3 servers hold incoming email messages until email is checked. After checking the email the messages are transferred to the user's computer. When the email is checked, messages are deleted from the server.

IMAP servers allow the user to work with email messages without downloading them to the computer first. The user can preview, organize and delete messages directly on the email server. Copies are stored on the server until deleted. Business email accounts commonly use this type of server.

SMTP servers handle the sending of email messages to the Internet. The SMTP server, which handles only outgoing email, is used in conjunction with a POP3 or IMAP incoming email server.

Since it has to support millions of users, an email server has to be fast, flexible and reliable.