The key difference between POP3 and IMAP is where the emails are stored. POP3 emails are stored on your computer, whereas IMAP emails are stored on the server*.
POP3 (Post Office Protocol)
This is an older but still widespread technology typically used on laptops or home PC's.
- Emails are physically downloaded from the server to your local computer or device. i.e. a single computer.
- Perfect for quickly downloading emails and reading them offline or on the go (remember that you need to be online to reply to emails).
- Any changes you make will not be seen by anyone else who accesses the email account as you are only making changes to the locally stored copies of emails.
- Outgoing emails are stored on your local computer until you "send" them via the email server.
- Great for locally archiving or storing your emails permanently on your local computer.
- As you collect (download) your emails your mailbox is being "emptied".
IMAP (Internet Message Access Protocol)
This is a newer and growing technology typically used by mobile devices.
- Multiple devices or computers can be used to access the emails stored on the server.
- Perfect for multiple users who need to access the same email account, or one user who needs to access emails from multiple devices or locations.
- Any changes you make (delete, reply, forward, move) are seen on any of your connected devices in real time.
- Outgoing emails are stored on the server (and can therefore be seen from all your devices) until you "send" them.
- You need to manually archive or store copies of your emails to your local devices as they need to be physically downloaded from the server.
- *As your emails are stored on the server you can soon "fill" your mailbox and run out of disk space.