Email Protocols and its
Importance
You get your new computer or laptop, and you need
to set up your email; be it Outlook Express, MS Outlook, or some other email
software. You know your email address and your password, so you follow the
steps, and still nothing happens. Then you see that the setup wants to know your
incoming server address and your outgoing server address.
Why do you need two? It
becomes more complicated when you don’t know anything and ask some friends for
help. One gives you an incoming server address beginning with POP3 while the
other gives you an address beginning IMAP4 – so which one is right. Yet both
give you an address beginning with SMTP for your outgoing
email.
Let us take a brief look
at what these different protocols are, what the differences are, why you need
them, and how they came about.
Let us forget about
web-based email services, where you are reading your email in your browser, and
concentrate on your email program; where you (or your software) regularly do a
“send and receive”.
How is email sent and
delivered
For a second, think of
old fashioned “snail mail”. You rent a post box at your local post office.
Someone sends you a letter from their local post offices, who deliver it to your
local post office. You go to the post office, open your post box with your key
and retrieve the letter.
So the email equivalent
is this: They send you an email via their ISP, who delivers it to your email
address (post box) at your ISP (local post office). Instead of riving their in
your car to go and collect it, you connect via the internet to your ISP (local
post office) and open your email account (your post box) using your user name
and password (your key). The email in your account is transferred electronically
into your Inbox in your email software.
Just as you cannot
deliver the mail directly into your friend's post box, but need to use the post
office to deliver it, so you cannot deliver the email directly to his account at
his ISP, but need your ISP to deliver it to his ISP marked with his
address. This is why you need to use an
outgoing server to send the email: your ISP mail sending
system. Your email account is held on a mail server at your ISP,
and your friend's email on one at his ISP. Email transfers between two servers are done via a
protocol called SMTP, which stands for Simple Mail
Transfer Protocol.
Just as you are a client
of your post office, so your email software (you) is a client of your ISP email
server (the post office).
SMTP is used to transfer
messages between two email servers (post offices). These servers need to be
permanently connected to the internet for delivery to take place. If you send an
email, and the recipients email server at their ISP is down for any reason, the
message will not be delivered. Instead you will receive a notification that the
email was undeliverable. SMTP is thus, only for transferring messages between
email servers, and not between email clients.
When you connect your
laptop or computer to your ISP mail server to download (collect) your mail, you
do so using an email client (such as Outlook) which connects to your account on
the mail server using one of two protocols. These are either the POP3 protocol
or the IMAP4 protocol. Some mail servers support both protocols, while others
support one or the other.
SMTP
The Simple Mail Transfer
Protocol developed with the birth of the modern Internet, or World Wide Web,
around 1980. Before this networked computers, mainly mainframes, used mail
protocols to transfer messages between themselves. With the birth of the
Internet, a universal protocol was developed from the various standards in use
before then. This universal standard became know as SMTP.
POP3
Probably, the most widely
used mail transfer protocol between the email server and the client,
POP3 stands for Post Office Protocol version
3.
This tells us that there
were two previous versions, with improvements in the protocol since it first
developed at the same approximate time as the SMTP protocol.
The Post Office Protocol
is essentially designed as a method for the client machine to connect to the
server, be authorized (authenticated) to obtain access to the email stored in
the user's email account, download these to the client's local computer, and
then delete them off of the server.
All of these messages are
delivered into a single folder, usually termed the inbox.
Recent improvements or
additions to the POP3 protocol, termed extensions, enable the user to choose to
leave copies of the downloaded email on the server for a specified period of
time. This is useful when you are operating on two computers (say home and
office) and need to download a copy of received emails to
both.
The POP3 protocol,
although the most widely used at the moment, is not as powerful as the IMAP4
protocol.
IMAP4
IMAP4 stands for
Internet Access Message Protocol, with the 4 telling us it is
the 4th version of this protocol.
The big benefit of
IMAP4 is that it maintains the messages on the server,
and synchronizes the messages on your local computer with that on the
server.
This makes it extremely
easy to keep more than one computer or laptop for email use, and have them all
totally synchronized. If you delete a message from your local machine, it
deletes it from the server when you synchronize. The next time you synchronize a
different computer, the server will inform it that the email is to be deleted,
and that computer or laptop will be updated accordingly. As a consequence, your
email on all the computers used to check mail will easily be kept up to date,
with changes made on one also reflecting on the other.
Another big benefit of
IMAP4 is that, it supports multiple folders. As a result, email received from
specific addresses may be received directly into specific folders, rather than
all lumped together in a general inbox. This saves time on email management, and
when your computer connects to the server, the downloaded messages will download
into the identical folders as they did on the server.
IMAP has not been around
as long as the POP protocol, having been developed in 1986. The initial protocol
was not compatible with all computers, which quickly lead to version 3 being
released.
Version 4 was released in
December 1994, with the current revision 1 of the IMAP4 protocol having been in
use since 1996.
Although IMAP4Rev1 (to
give it the full title) is largely backward compatible with older versions,
there are very few of the older versions still in use.
Which should you use?
Most email servers are compatible with POP3, and many of them not with IMAP4, so
your decision will largely be made for you by your ISP. However, if you do have
the choice of either (your ISP supports both) then decide based on the features
that you personally need.
Currently, IMAP4 is more
widely used on Web Based email servers such as Google Mail, and if you have a
Gmail account and wish to download messages to your laptop, you are going to
find yourself using IMAP4
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