What’s the difference between POP and IMAP?

If you are confused about the difference between POP and IMAP, here is a summary of the advantages and disadvantages of both which will, hopefully, allow you to make an informed choice when setting up your email account in your preferred email client software like Thunderbird or Outlook.

POP advantages

• messages load very quickly once they’re downloaded
• messages are stored on your hard drive so they’re not subject to server storage limits and quotas
• it is widely supported by ISPs and email providers
• all email programs support it

POP disadvantages

• messages are stored on your hard drive so they’re not accessible from other computers
• sent mail and drafts are not accessible from other computers either
• messages are eventually removed from the server
• messages are stored in files that are not compatible between different programs
• it’s usually difficult to migrate from one program to another, sometimes impossible
• it’s cumbersome to copy your email to another computer, e.g. office - home - school - laptop etc. (unless you use Thunderbird which makes it very simple)
• users normally don’t have backups of their email

IMAP advantages

• messages are stored on the server are accessible from any computer and webmail anywhere in the world
• IMAP mail folders remain synchronized with your webmail
• sent messages and drafts are also stored on the server
• server-side spam filtering is easily implemented with IMAP
• IMAP mail is backed up nightly on the server and can be restored
• ease of migration from a program to a program and from a computer to another computer/location
• ease of setting up additional computers to check your email, no need to copy anything from one computer to another

IMAP disadvantages

• messages load slower, in particular the first time they’re read
• sensitive to size and requires periodic archival of email messages
• subject to storage quotas
• very few ISPs and email providers offer IMAP as it is considered a high end option and it’s complex for them to support
• not all email programs support it properly

If you start using IMAP you should no longer use POP for that email account on any other computer! Using a mix of POP and IMAP will lead to conflicts and will basically defeat the purpose of switching to IMAP in the first place. To get the the full benefits of IMAP you must switch to IMAP exclusively on all computers you intend to check that email accounts on. It’s OK to continue to use webmail as it is essentially an IMAP client.