POP3 and IMAP Email Protocols
A brief overview of the POP3 and IMAP email protocols and how to choose which to use.
These are two different Internet protocols designed to provide access to e-mail. If you are using an email client (like Outlook), the software has to use either one of these to access your emails and download them to your computer. If you only ever use webmail to access your emails you don’t have to worry as these protocols are not used.
When someone sends you an email, it will be stored on a mail server somewhere on the Internet. If you use webmail, this looks directly at the emails on this mail server. To see the email in Outlook (for example) the email has to be collected and stored on your computer. This is where POP3 and IMAP come in.
POP3
POP3 works by downloading the whole email onto your computer and then removing the email from the mail server because it is not going to be accessed again. If you were to use webmail to look at your emails after downloading using POP3, the email will no longer be there in webmail.
It is possible to set Outlook to download AND leave the email on the mail server. There are a few times when this is needed (for example to work with a Blackberry account) but in general this is bad practice because Outlook will try and download the email again and again. If you do need to do this, make sure you also set the emails to be removed after a few days.
IMAP
IMAP is designed for situations where you have more than one method of accessing your emails, usually when you want to read and send emails from different locations or different devices. For example, you may want to access your email on your mobile phone or PDA as well as your computer. You may also want the facility to check emails using webmail from other locations like Internet cafes.
IMAP works by downloading emails but leaving them on the mail server until they are deleted. Each time a device accesses the emails, it synchronises any changes made so, if you delete an email using your phone, your computer will update its copy and delete this too. IMAP can also be set to download just the first part of an email (the email header) so you can decide if you want to download and read the whole thing.
IMAP can work with folders too so you can organise your emails into groups.
The main difference is that POP3 is designed to download the email and then remove it from the mail server, whereas IMAP leaves emails on the server to be accessed again from another device or by webmail.
In general if you only ever access your emails on your computer, or perhaps just use webmail occasionally to view new emails when away from the home or office, use POP3.
If you want to use more than one device (computer, phone, PDA), or if you need to access all your emails from webmail, not just the new ones, use IMAP.