Oct 042014

What do POP and IMAP mean?

The @ sign and a question mark mergedThese are both methods or “protocols” used by email programs (also called “email clients”) so that the email program and the mail server (the computer that deals with your email) can understand each other and deliver your email. “POP” stands for “Post Office Protocol” and “IMAP” stands for “Internet Message Access Protocol”.

These protocols are only concerned with INCOMING email and they are only relevant if you deal with your email by using a program on your own computer or device. In other words, email protocols are not relevant if you connect to your mail server by logging onto a website (this is known as webmail). Some of the most popular email clients are:

  • Outlook
  • Windows Live Mail
  • Apple Mac Mail
  • Thunderbird
  • Outlook Express used to be a very widespread email client. It is no longer available, having been replaced by Windows mail and then Windows Live Mail

What is the difference between POP and IMAP?

With POP email (or, more likely, its latest incarnation – POP3) your email is downloaded from the mail server onto your own computer. After that, it may remain on the server or it may be deleted from the server either immediately or at some later time – eg one week or one month later.

With IMAP email, your email is stored on the mail server. It remains on the server until/unless you delete it.

What are the implications of the difference?

Harry Hill mouthing "fight" under a headline of "POP vs IMAP"With IMAP you can create email folders and sub-folders on the mail server itself. You can not do this with POP email. The folders and sub-folders you create with POP are on your own computer and only on that computer. So, if you check your email from lots of different places (eg a laptop at home and a smartphone and tablet when on the move) you can not see all of your folders if you use POP unless you manually replicate the folder structure on all your computers and devices. Moreover, you will need to do your filing into folders on each computer and device separately. With IMAP, on the other hand, the folder structure is created once on the server and then every device that you connect sees the same structure.

Another major difference is that when using POP email your “sent” email is not available on the server. The sent mail is stored on the computer or device that sent it. This has the drawback that you can not see on one computer the email that you sent from another computer. The way around this is to send a blind copy (a BCC) to yourself. This will arrive in the inbox of all your computers and devices. You can then move it to the “sent” folder on that device. This can be time-consuming and tedious.

If IMAP always shows all email in the same way to all computers and devices, why would you use POP instead?

POP vs IMAP - clipartThe main drawbacks of IMAP are speed and data file sizes Every time you open your email, the program has to synchronise the headers that you see at your end with the reality of what’s on the server. This can take time. Also, if you always file email rather than deleting it then your online store of emails is getting bigger all the time. It’s possible that your email provider only provides you with a specific amount of storage space. You could reach the limit. So, over time IMAP can become unwieldy.

There is also the aspect that I think of as “perceived control”. A lot of people are unwilling to trust that data stored “in the cloud” will always be available to them. They feel more secure knowing that all their data is stored on their own computer. For such people, POP email feels more safe.

Another factor that might sway the choice towards POP is that most people typically have one computer that they think of as containing everything and being their “main computer” or “mission control”. These people wouldn’t be expecting to see, or need, all their “sent” email on their smartphone, for instance. The mobile devices are more useful for just staying on top of what is coming in – not for storage. If an important message does need to be sent from a mobile device then a blind copy can always be sent to oneself for subsequent filing on the “main” computer.

Can I choose which to use?

It’s just possible that your email provider will not be able to provide IMAP. In that case, it’s POP or nothing. In reality, most email servers now offer a connection by either protocol.

PS: apologies for the rather odd email sent in my name in the middle of last week. This must have been triggered when I was trying to change my newsletter details to reflect the new “.london” domain name.

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Computer Support in London
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