Overview
POP3 and IMAP are two separate protocols to access e-mail stored on the server. POP3 originated first in 1996 and IMAP in 2003. POP3 is designed for devices that have limited Internet connectivity and limited storage available on the mail server. POP3 is suitable for a dial-up connection or situations in which limited storage is available for e-mail. Thankfully, those days are long behind us.
IMAP evolved in conjunction with persistent online connections, like cable modems and DSL. IMAP keeps e-mail on the server and synchronizes its status (read, replied-to, forwarded, labels) with every e-mail client that accesses the server. This makes it suitable for access from phones and desktop mail clients: reading a message on your phone will synchronize its status with your desktop and vice-versa.
Key differences
IMAP and POP3 are drastically different protocol implements. While they both access e-mail, IMAP and POP3 access mail with different behaviors as outlined:
| IMAP | POP3 | |
|---|---|---|
| Mail storage | Mail resides on server | Mail resides on computer |
| Synchronization | Yes, mail is synchronized across all devices | No, mail is removed from server once accessed* |
| Sent mail | Saved on server | Saved on desktop |
| Deleted mail | Sent to Trash folder, Trash must be “emptied” in mail client to free storage | Does not free storage; removed from desktop |
| Disaster Recovery | Yes, through Lithium Hosting | No |
| Access e-mail without Internet | No, requires Internet connection | Yes, does not require Internet connection |
* POP3 can be configured to leave mail on server once downloaded, this will result in duplication of mail across multiple platforms and is not recommended. Use IMAP in this instance.
Which is right for me?
IMAP, unless you have limited Internet connectivity and must have access to e-mail at all times. In such extreme scenarios, then POP3 is a better choice.