What is IMAP vs POP?

Many ask for clarification about IMAP email vs POP email and what direct impact these technologies have upon the daily workflow.  To over simplify, the difference is merely where your mail is stored.  With IMAP (Internet
Message Access Protocol), your mail is always stored on the mail server and your various devices merely talk to the mail server to read what is there, but they leave it there.  With POP3 (Post Office Protocol) your mail gets downloaded to your local device and removed from the server.

Technical details aside, the technology to use is dependent upon how you need to access your mail and what your storage requirements may be.  IMAP is great when there are many devices and you want to ensure each device has the ability to see what is on the server.  All the mail stays on the server, so any device can always see what is there.  The same goes for your sent mail, trash, junk mail, etc; all of those folders you create will stay on the server.

POP is great to reduce the storage space on the server.  In this age, many email messages contain attachments that are large and can easily fill up storage space on a mail server.  Even with larger mail quotas of many gigabytes, our email can quickly fill up the available space.  POP is recommended in this situation to download those messages locally and free up space on the server.

The next question would be how do you decide which to use?  The good news is that you can use both!  These technologies are not mutually exclusive.  In fact, we recommend both of these to our clients.  The ideal situation is to have one primary system (your main desktop or laptop computer) be setup to use POP3 and store all your mail locally on its main drive.  This ensures that mail will be downloaded from the server by at least once device and stored so you have access to it, as well as your own local backups.  The rest of your devices, whether it's another laptop, a tablet, phone, etc, should all be configured to use IMAP.  It is not ideal to have more than one device setup as POP as then you no longer have your one, primary source of all your email. 

The next question is this: if you have a computer setup to download mail and delete it remotely (POP), then how would another device see that mail later (IMAP)?  The secret to making this all work lies in the configuration for your POP setup.  You need to find a mail client that allows you to "leave a copy of mail on server" for a period of time.  Depending on your mail traffic, you may set this to a month or two, or even a year.  This ensures that eventually the mail will be removed, but you can leave that copy there for a while so all your IMAP devices can access it.  This is the best situation because it keeps your mail storage quota from running out while still giving all your devices access to mail while on the go.

Here is one possible page about how to configure your POP settings on various email clients to leave a copy on the server, but please search around -- there are lots of articles on how to do this!