1. Mail Server Mail is just a message in any form sends from sender to receiver. Mail Server is a computerized system that is equivalent to virtual post office. Every mail that is sent passes through a series of mail servers along its way to its intended user. Early email system required both receiver and sender to be online. Today’s email system uses store-and-forward model(neither user nor their computers are required to be online simultaneously.

2. PROTOCOL USED: Mail server sends and receives email using standard email protocals. 1. SMTP (Simple Mail Transfer Protocol) 2. POP(POST OFFICE PROTOCOL) 3. IMAP(Internet Message Access Protocol)

3. HOW MAIL SERVER WORKS?

4. Suppose user A(Nepal) wants to send mail to user B(USA) then will be numerous mail server between them. When user A sends mail then user B donot receive it directly but will follow below steps. First user A sends mail to its nearest mail server via SMTP protocol, then this server sends to its nearest server via SMTP and this process continue until mail reaches to the mail server nearer to user B. After that,that mail server sends mail to user B via POP OR IMAP Protocol. Same happen if user B sends mail to user A. So,SMTP is outgoing protocol as it can send but cannot receive, and POP/IMAP is incoming protocol as it can only receive but cannot send.

5. Port uses: SMTP :25 POP:110 IMAP:143 POINT TO BE NOTED!!!!!!!!!!!!!! If you want to receive your mail message only on one single computer or device,then POP is useful because when email client accesses server then it download all your mails to computer then message is deleted from server. Used by: OUTLOOK EXPRESS While using IMAP, we can access your mails on multiple devices simultaneously at any time because IMAP allow to client to view his/her mail and keep it in server.(NOTE: SERVER WILL NOT DELETE THIS). Used by :Gmail, Yahoo, Hotmail,facebook messanger etc.

6. POP doesnot require an Internet Connection, if you want to access the downloaded emails, unless you want to retrieve new emails. while IMAP which stores your emails in cache only requires internet connection all the time.

7. WE CAN CREATE OWN MAIL SERVER? In order for a computer system to function as a mail server, it must include mail server software. This software allows the system administrator to create and manage email accounts for any domains hosted on the server. For example, if the server hosts the domain name “tech.com," it can provide email accounts ending in "@tech.com.“.software domains domain name Then email id will be like this : diwas16@tech.comdiwas16@tech.com teambit@tech.com@tech.com gopal@tech.com