IMAP vs. POP3

The fundamental difference between IMAP and POP3 lies in how and for how long mail is stored on the mail server.

When POP3 is used, messages are deleted from the mail server when they are downloaded. That means that the messages are then only accessible from the computer to which they have been downloaded. While this conserves your mail server’s disk resources, it limits how your users can access their email. It may also be important to note that POP3 does not require a constant connection while email is being read.

When IMAP is used, messages are stored permanently on the mail server. This means that they can be accessed by any number of computers as long as the user has the correct login information. While convenient, this method generally requires more dedicated disk space due to users not deleting old mail. The IMAP courier, however, is still viable on a mail server with low resources as long as users monitor their disk usage and delete old messages when necessary. It may also be important to note that IMAP requires a constant connection while email is being read.

IMAP is generally preferred amongst web hosts and users due to its convenience. Carefully consider your system’s available resources before choosing either courier.