An email server is a general term for hardware and software facilities that handle email exchange, including email programs, email boxes, etc. It is an email system that provides users with full E-mail services, and people exchange emails by accessing the server. The server program usually cannot be started by the user, but is always running in the system. On the one hand, it is responsible for sending the E-mail sent from the machine, on the other hand, it is responsible for receiving the E-mail sent by other hosts, and sending various Emails are distributed to each user.

There are several types of email servers:

1. SMTP server

The SMTP (Simple Mail Transfer Protocol) server is a server that sends emails, and it is responsible for delivering emails from the sender to the receiver's mail server.

2. POP3 server

The POP3 (Post Office Protocol version 3) server is a server for receiving e-mails. When a user uses a mail client program (such as Outlook) to download mail, the POP3 server will download the mail from the mail server to the user's computer.

3. IMAP server

The IMAP (Internet Message Access Protocol) server is also a server for receiving e-mails, but unlike POP3, the IMAP server will not download the e-mails from the mail server to the local computer, but save the e-mails on the server. You can view it on the terminal.

4. Webmail server

Webmail server is a web-based email system. Users can access the Webmail server through a web browser to send and receive emails without installing any mail client program.

5. Exchange server

Exchange server is an enterprise-level mail server. It can not only send and receive emails, but also manage information such as calendars, contacts, and tasks, and provide sharing and collaboration functions.