Email Tutorials

What is Mail Server and How Does it Work?

Sending a mail is easy, click the send button and your message is delivered to anyone situated anywhere in the world in seconds. Have you ever thought about the procedure of mail delivery? Read on to learn everything about mail server.

What is a Mail Server?

A mail server is also known as Mail Transfer/Transport Agent or an Internet Mailer or Mail Router at times.

Wondering what is a mail server? Just like a mailman delivers letters to your home, a mail server also performs the same job responsibilities. An email sent to someone has to pass through several mail servers before it can reach its recipient. You would be unable to send mails to those whose email addresses don’t match your domain, if mail servers were not there.

A computer that is exclusively used to run applications which receive emails from people with the same domain and sends it out for delivery are mail servers. Some common mail server programs are qmail, Exim, Microsoft Exchange and sendmail.

Mail server functions in unification with other programs to form a messaging system. This messaging system comprises of all important applications that are required to move an email in its intended direction. For instance Outlook will forward the message to your mail server which will then forward it to a different mail server or to a holding area in the same server which is referred to as ‘message store’ which will be forwarded later.

What follows is a better understanding of these different types of mail servers so you know in detail, what is a mail server all about.

Different Types of Mail Servers

There are basically two types of mail servers:

  • Outgoing Mail Servers
  • Incoming Mail Servers

Outgoing Mail Servers:

Also known as Simple Mail Transfer Protocol or SMTP servers, the main function of an outgoing server is to look after the delivery process of all the email that you send across by transferring them from your webmail to the inbound server from where the person who you have directed the mail will pick it up.

Incoming Mail Servers:email-server1

There are mainly two types of servers in an incoming mail server that are

  • Internet Message Access Protocol or IMAP
  • Post Office Protocol or POP3

The internet service providers usually give a POP3 address to their users. In order to collect mail from an incoming mail server verification is needed which is done in the form of email address and the connected password. There could be a registered password assigned just for the mail or a password that has been allocated to the account. A POP3 mailbox can be accessed by a single person at a time and after it has been retrieved the server deletes it automatically.

Although POP3 is good sometimes it isn’t all that beneficial. The IMAP however allows collecting the email and leaving a copy of it too. This is easy for those who retrieve mail from multiple locations such as with IMAP a user would be able to retrieve personal emails when he is at work to be updated about things and then delete them from the office system and retrieve it again from home so he can reply to them. One can configure the home email client so that the emails can be deleted from the server. People using Personal Digital Assistants, smartphones, tabs or iPads that have email access and IMAP support can also check emails without having to delete email from the server.

There could be some emails that can be easily answered with a thumb keypad but there could be emails that need time and the convenience of a proper keyboard to be replied which can be done later. An IMAP protocol also has other uses; emails on the incoming mail server can be marked to show different states like a retrieved email can be marked as having read.

POP3 is usually linked with ISP mail service whereas IMAP is normally used by Web based email services. IMAP is quite flexible and it can be used with POP3 accounts, provided an IMAP supported email client is used. Good email clients will offer support for both IMAP and POP3 protocols.

Process of Sending an Emailemail-server3

Below is the process of sending an email:

  1. Once you click the send button the application will connect to the domain’s SMTP server.
  2. The email client connects with SMTP server and gives the receivers email address, senders email address, attachments and message body to it.
  3. The SMTP will then process the receivers email address and domain. In case the senders domain is same as the receivers the message is channelled straight to the domain’s IMAP or POP3 server. In case the receivers domain is different the SMTP connects to the required domain’s server.
  4. To locate the receivers server the SMTP server of the sender will connect to the DNS which in turn uses the receivers email domain and converts it to an IP address. SMTP of a sender will be unable to channel an email just with a domain name and an IP address is required. An outgoing mail server will function efficiently if this unique number of the system is known.
  5. Once the SMTP server obtains the IP address of the receiver it connects to the SMTP server of the receiver. A message is channelled through many discrete SMTP servers before it can connect with its destined server.
  6. The SMTP server of the receiver will scan the incoming message and forward it to the domains IMAP or POP3 server once it recognises the user name and domain. The email sits in the sendmail queue till the receiver downloads to read it.

Even though an email sent takes a no more than a few seconds to reach the person you have sent it has to go through the above intricate transfers before it is delivered to the right person, this is what is a mail server all about.

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