What is a Mail Server?
The Process of Sending an Email
With the click of a
mouse button, you can send an email from one point of the globe to another in a
matter of seconds. Most of us take this process for granted, giving little
thought to how it actually works. It's easy to understand how standard
snail-mail gets from point A to point B - but how does an email message make
its way from a sender to a recipient? The answer to that question revolves
around something called a mail server. You can learn more about the role that
mail serves play in email delivery by reading on below.
What is a Mail
Server?
A mail server is
the computerized equivalent of your friendly neighborhood mailman. Every email
that is sent passes through a series of mail servers along its way to its
intended recipient. Although it may seem like a message is sent instantly -
zipping from one PC to another in the blink of an eye - the reality is that a
complex series of transfers takes place. Without this series of mail servers,
you would only be able to send emails to people whose email address domains
matched your own - i.e., you could only send messages from one example.com
account to another example.com account.
Types of Mail
Servers
Mail servers can be broken down into
two main categories: outgoing mail servers and incoming mail servers. Outgoing
mail servers are known as SMTP, or Simple Mail Transfer Protocol, servers. Incoming mail
servers come in two main varieties. POP3, or Post Office Protocol, version 3, servers are best known for
storing sent and received messages on PCs' local hard drives. IMAP,
or Internet Message Access Protocol, servers always store copies of messages on
servers. Most POP3 servers can store messages on servers, too, which is a lot
more convenient.
The Process of Sending an Email
Now that you know
the basics about incoming and outgoing mail servers, it will be easier to
understand the role that they play in the emailing process. The basic steps of
this process are outlined below for your convenience.
Step #1: After
composing a message and hitting send, your email client - whether it's Outlook
Express or Gmail - connects to your domain's SMTP server. This server can be
named many things; a standard example would be smtp.example.com.
Step #2: Your email
client communicates with the SMTP server, giving it your email address, the
recipient's email address, the message body and any attachments.
Step #3: The SMTP
server processes the recipient's email address - especially its domain. If the
domain name is the same as the sender's, the message is routed directly over to
the domain's POP3 or IMAP server - no routing between servers is needed. If the
domain is different, though, the SMTP server will have to communicate with the
other domain's server.
Step #4: In order
to find the recipient's server, the sender's SMTP server has to communicate
with the DNS, or Domain Name Server. The DNS takes the recipient's email domain
name and translates it into an IP address. The sender's SMTP server cannot
route an email properly with a domain name alone; an IP address is a unique
number that is assigned to every computer that is connected to the Internet. By
knowing this information, an outgoing mail server can perform its work more
efficiently.
Step #5: Now that
the SMTP server has the recipient's IP address, it can connect to its SMTP
server. This isn't usually done directly, though; instead, the message is
routed along a series of unrelated SMTP servers until it arrives at its
destination.
Step #6: The
recipient's SMTP server scans the incoming message. If it recognizes the domain
and the user name, it forwards the message along to the domain's POP3 or IMAP
server. From there, it is placed in a sendmail queue until the recipient's
email client allows it to be downloaded. At that point, the message can be read
by the recipient.
How Email Clients
are Handled
Many people use
web-based email clients, like Yahoo Mail and Gmail. Those who require a lot
more space - especially businesses - often have to invest in their own servers.
That means that they also have to have a way of receiving and transmitting
emails, which means that they need to set up their own mail servers. To that
end, programs like Postfix and Microsoft Exchange are two of the most popular
options. Such programs facilitate the preceding process behind the scenes.
Those who send and receive messages across those mail servers, of course,
generally only see the "send" and "receive" parts of the
process.
At the end of the
day, a mail server is a computer that helps move files along to their intended
destinations. In this case, of course, those files are email messages. As easy
as they are to take for granted, it's smart to have a basic grasp of how mail
servers work.