Nearly every business these days relies upon email for both internal and external communication. Email is now commonly used at work, at home and on people's phones. Whether you use webmail, your ISPs email service or your own email system email is more complicated than you might realise.

You may have seen in your incoming email settings on your computer or phone the terms POP and IMAP. These are the protocol (or language) used to communicate with your email server.

Post Office Protocol (POP)

POP is the older of the two protocols commonly used for the retrieval of email. It's first edition dates back to 1982 with the current version (version 3) dating back to 1988.

Back when POP was created, computers (including mail servers) had only low bandwidth access and very limited storage so it was decided to create a protocol which downloaded copies of emails which could be read offline and to delete those emails from the server.

POP is an adequate solution until you need to access your email on multiple devices. In order to access your POP based email on other devices you need to make sure that each device is set to leave mail on the server. If one device isn't set properly it will grab all your mail and delete it off the server so it can't be accessed on any device which may access it after. Even when your mail is kept on the server, each device you access it from will download your email and show it as being unread (even if it has already been read). If you have organised your mail into folders or deleted it, this won't be reflected on any device other than the one on which you did it on. This can be quite frustrating and time consuming - having to re-read and re-organise emails.

Internet Message Access Protocol (IMAP)

IMAP is the newer protocol of the two. It was designed in 1986 and has gone through a number of revisions until the current version (version 4) in 1994.

IMAP differs from POP by allowing users to access their emails from multiple devices and view the same emails because they are stored on email servers until the user deletes them. Because the mail is stored on the server, when you read an email on one device it is marked as read on every device, when you organise your email into folders, those emails and folders are the same on each device.

Where it is now common to check email via web interfaces, email applications and on mobile phones, IMAP has become the protocol of choice.

The major disadvantage with IMAP is that the size of your mailbox is constrained by your allocated quota on the server. In the case of POP, you can have mailboxes the size of your hard disk because the emails are kept locally.

Which should you use?

In most circumstances IMAP is the more appropriate protocol to use due to its support for multiple devices and its ability to keep your mailbox the same across devices, however, if you expect to keep a huge history of email you might want to use POP to keep space free on your email server.