What is the difference between POP and IMAP?
Illinois State University email servers support two email protocols: POP and IMAP. This overview will help you decide which email protocol is best suited to your needs.
What is an email protocol?
The email protocol you choose will determine where your email is stored—on the server or on your computer. When configuring an email client, such as Mozilla Thunderbird or Microsoft Outlook, you should choose an email protocol that best suits your needs.
IMAP—Email Stored on the Server
IMAP is recommended for most people. IMAP keeps your email on the mail server so you can access it from multiple locations and with multiple email clients. For example, you can see the same email at home and at work. Likewise, you can see it in RedbirdMail and Thunderbird.
IMAP is not suited to offline use. If you need to see your email when you are offline (i.e. not connected to the Internet or the campus network), you should consider using POP instead.
- IMAP stores your email on the mail server
- IMAP allows you to read all of your email in multiple locations.
- IMAP will only allow you to view previously read messages when offline; messages previously received (but not read) are not viewable when offline.
- Checking email with IMAP may be faster than checking email with POP.
POP—Email Stored on Your Computer by Your Client
POP is recommended only for people who need to access their email offline. If you need to connect to the Internet, download your email, and then disconnect, POP is a good choice for you. However, POP has a few important limitations of which you should be aware.
POP stores your email on your computer in your email client (i.e. Thunderbird, Outlook, or whatever program you use to check email). When you check email, it is downloaded to your email client and removed from the mail server. This is why you can read your email when you're offline—because the email is actually on your computer you don't need an Internet connection to see it.
With POP, you cannot see email you previously received when you use other computers or other email clients, including RedbirdMail. If you receive an email message at home using Outlook configured for POP, you won't have access to that same message when you go to work. Likewise, you won't be able to see it in RedbirdMail or any other program.
- POP removes your email from the server and places it on your computer.
- POP does not allow you to view previously received email from other locations.
- POP allows you to read previously received email and attachments when offline.
- Checking email with POP may be slower than checking email with IMAP.