How Does An Email Server Work?

Sending and receiving emails is something that is done in such a mundane manner that we never stop to think how this automatic, quick mail communication takes place. The key element in email communication is the email server. There is a very interesting technology behind the functionality of the email server.

Basically, email communication is made possible by SMTP and POP3 or IMAP server types. The most widely used mail-client software is Microsoft Outlook or Mozilla Thunderbird, and Mac OS X’s Mail. All these email software packages perform the same function, which is downloading incoming email into the machine from the mail server of the concerned email account like Yahoo, Gmail or AOL.

Communication that occurs on the internet is through the client-server connectivity. In simple terms, the client is the computer connects through a unique internet protocol address through the internet and the server is another computer connected to the internet which takes care of hosting and serving web pages. Servers are nothing but computer programs that run on high speed machines. These high speed machines are designed in the manner that they handle the requests of millions of clients. All the requests are served at the same time to those who access an email or webpage. This process is called web hosting.

Whenever an email is sent out, the system connects to your email service’s mail server which is a centralized computer that manages a specific service. For instance an email server handles emails. This email server which is responsible of sending email is called Simple Mail Transfer Protocol (SMTP) server. The SMTP server passes the mail to another SMTP server to the destination through several hops. Every email has the sender’s and recipient’s address. When an email is sent, the client connects to the SMTP server of the sender’s email service. The address of the sender, recipient and the content of the message is transmitted by the client. The SMTP locates the recipient’s whereabouts.It locates the domain name by recipient’s mail ID. This process will be simple, if the recipient’s mail ID has the same domain as the sender.

Each domain refers to a unique web address known as Internet Protocol (IP) address. The link between domain names to their IP address is stored in the Domain Name Registry. The SMTP server contacts the DNS server where the registry is stored. The address is sent back to SMTP server by the DNS server. The SMTP server sends the email to the SMTP server of the recipient’s email service. This server ensures the mail address of the recipients belongs to it and hands over it to the POP3 or IMAP server.

POP3 servers store our email IDs. Each mail account is associated to a username and password. Till the recipient log in and check the mail, the message in the POP3 server is kept and stored in the mail account

An email client which connects to the POP3 serve tell it to allow email for download..Pop3 mailboxes do not hold a copy of email once the mail is downloaded in the local machine and hence once cannot check the mail again the downloaded already from another machine. In order to overcome this issue IMAP4 (Internet Message Access Protocol version) was introduced which retains a copy of the emails on the server. This allows accessing the email from any location. Now a days MIME (Multipurpose internet Email Extensions) supports audio and video attachments in the email. Thus a simple principle lies on the working of the email system, it handles millions of request through out the world making this as one of the most advanced mailing system.