POP3 vs. IMAP
Advantages of POP3
- Retrieved messages are available when offline
- E-Mails are not stored on the server, so disk usage on the server is less
- Simpler protocol and easier to implement
- More supported client software
Disadvantages of POP3
- Messages retrieved one computer cannot be retrieved again from any other computer
- Much harder to do server-side filtering
- Can be much slower to check mail
Advantages of IMAP
- Mail is accessible from multiple computers any time, simultaneously, and anywhere
- Mail is stored on the remote server, so email cannot be deleted/destroyed if your computer should happen to crash, be stolen, or destroyed
- IMAP mail can be accessed via the web, without even needing a mail client installed. This means you can check your mail from someone else's machine or even a public terminal without needing to set up or configure any third-party software
- IMAP provides a mechanism for a client to ask the server to search for messages meeting a variety of criteria. This mechanism avoids requiring clients to download every message in the mailbox in order to perform these searches
Disadvantages of IMAP
- Mail is not usually available if you are offline
- Implementing IMAP is more difficult and error-prone than implementing POP3 for both client and server implementations. This can result in security issues which are less likely under POP3
- IMAP generally results in higher server loads than POP3, resulting in higher costs for ISPs and end users
- Server side searches can potentially use lots of server resources when searching massive mailboxes