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Understanding Email Protocols

There are four basic ways to get Email:
  1. WebMail
  2. POP3
  3. IMAP
  4. Microsoft Exchange

This will help you choose the ones that are best for you.

If you use a browser, to view your mail at Gmail, or Yahoo or AOL, then you are using Webmail. With Webmail, you are peeking at you emails on their server. Just like visiting a news site. You are looking at what is on their site. You handle the mail there. You send and receive messages using their system on their computer. If you want to make a backup of your email, you must figure out how to get it off their server. If your email account gets too large, they may delete your emails or otherwise restrict you. They are controlling your mail, but letting you use their server. It is important to determine how they make their money. Somehow they are turning your usage of their system into profits that exceed their costs.

This system makes it easy to be mobile, but isn't a safe way to preserve your mail and isn't secure. If maintaining your email or some of it is critical to you, then you must figure out how to download it from their servers, what format it gets downloaded as, and how you will access your local backup.

POP stands for Post Office Protocol. With this system, your email client (like Thunderbird, Outlook or Intellect) logs into a server that holds your email and picks it up. Then stores it on your computer, normally, deleting it from the server. This is just the opposite of Webmail. It is like going to a post office box and collecting your paper mail. You have it. The post office does not keep it.

Whether you use Gmail, Yahoo, AOL, Comcast, or your Website host to collect your mail for you, it works the same way. They hold the email until you pick it up, then delete it. It is possible to configure your mail client to instruct the host to keep your mail for a couple of days (or more) instead of deleting it right away. But, the mail is kept on your computer and you can back it up. You are also responsible for it. If you don't back it up, and you lose your computer or storage, then you will lose your emails. You will again be responsible to transfer the saved messages to a new computer when you get one.

Even if you have an Email client using POP3 on your computer, you can still access your email via Webmail with your browser. You will only see the messages left there by the POP3 Email client.

POP3 controls how that particular program will interact with the Mail server. It does not prevent your browser from accessing the email via Webmail. But, if you have already downloaded email with your POP3 client, those emails won't be available via Webmail.

The problem with POP3 is that mobile users end up using a phone or laptop and not seeing the emails they previously downloaded on their desktop computers. They only see the emails that came after they downloaded the emails to their desktop computer.

IMAP tries to give you the advantages of both a local email client and Webmail. IMAP stands for Internet Message Access Protocol. With IMAP, your email client peeks into the server, like Webmail, but downloads your email, like POP. IMAP synchronizes your local email client with the server and the server with your local client. So, if you get your email at the office using IMAP, and then go home and check it with your laptop, the same emails will be available on the laptop. If you respond to an email and delete another email, then that is reflected on the server. The email you deleted will be deleted from the server. The email you sent will be added to the sent folder on the server. When you login with your office computer, it will delete the deleted email from your local computer and add the sent email to your sent folder. Now all three computers, home, server and office are the same.

Microsoft Exchange
Microsoft Exchange is like IMAP, done Microsoft's way. The emails remain on the server and synced to your local computer(s).

Important factors

  • If you want to be sure you have a local copy of all your mail, POP is easier. IMAP messages may not be completely loaded onto your local computer as often they only download headers. Each IMAP server can implement its procedures its way and each client can have theirs. Most Email clients can mitigate this issue. They will give you some way to force emails to be downloaded. In the same way, most email clients give using POP3 allow you to save messages on the server for some length of time.
  • POP allows you to merge multiple mail accounts into a single Inbox while they are kept separate with IMAP.
  • IMAP is the right way to have everything available on multiple machines.
  • Mailbox limits can adversely affect Exchange and IMAP accounts with Mailbox full limitations. This can also affect POP clients if you set your client to not delete emails from the server.


Regardless of what system you use, examine your storage requirements, both access to old emails and backup of your data. You need to be sure the system you have meets your needs.

Date: October 2018

Creative Commons License
This article is licensed under a Creative Commons Attribution-NoDerivs 3.0 Unported License.

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