Tech Guides :: Email :: Which to use? POP vs. IMAP
What is an email protocol?
Merriam-Webster defines protocol as "a set of conventions governing the treatment and especially the formatting of data in an electronic communication system."
So, an email protocol governs the rules for the treatment and storage of email messages. While each email protocol offers an assortment of options and characteristics, its most important aspect is this:
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 Eudora Pro or Outlook, you should choose an email protocol best suited to your needs. If you install Eudora Pro as a part of Internet Tools, you will not need to choose an email protocol. Instead, these applications will automatically be configured for you, based on your choices during the installation.
IMAP: Internet Messaging Access Protocol
The IMAP protocol is best for people who check email on multiple computers. If you plan to check email on a single computer, you may want to consider the POP protocol (see below).
IMAP works differently than POP, in that IMAP will always store permanent copies of your email on the mail server. When you check email, IMAP will download temporary copies of new messages to your computer, but will leave permanent copies of the messages on the mail server.
Because your email is always stored on the mail server, you can read it when checking email in multiple locations. For example, if you check email at home and receive five new messages, those messages can also be read when checking email in a campus computer lab (or in your office, etc.).
As mentioned above, when checking email using IMAP, only temporary copies of those messages are downloaded to your computer. Due to the nature of these temporary copies, checking email in IMAP may be slightly faster than checking email using POP.
Additionally, you may be unable to read previously received messages when offline (i.e. not connected to the Internet). For example, if you received five new messages, but only opened one of them, the remaining four messages would be unreadable when offline.
- IMAP always 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 using IMAP may be slightly faster than checking email using POP
At Humboldt State, email clients such as Eudora Pro and Outlook can be configured to use the IMAP email protocol. Webmail always uses IMAP. This means that if you configure your email client (i.e. Eudora Pro) to use IMAP, you will see the same messages in Eudora Pro, Webmail.
POP: Post Office Protocol
Simply stated, POP is good for people who only check email on one computer. If you check email in multiple locations, you may want to consider IMAP (see above).
As its name implies, the POP email protocol works like a post office. When someone sends you an email message, it is received by the mail server, just as when someone sends you a letter, it is received by your local post office. The post office (like the mail server) holds your message until you ask for it (by checking email).
When you check email, your messages are removed from the mail server and placed on your computer. Like the real post office, the mail server does not keep copies of your messages.
If you check email in another location, such as a campus computer lab, you will not see any email previously received. Whenever an email client is told to check email, it looks to the mail server to see if any new mail is has been received.
Since POP downloads email to your computer and removes it from the server, your old messages cannot be seen from another location. They are not being stored on the mail server any longer; they are being stored on your computer.
Because your email is stored on your computer, you can read previously received email when you are offline (i.e. not connected to the Internet). Likewise, you can open and use previously received attachments while offline.
- 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 use previously received attachments when offline
At Humboldt State, email clients, such as Eudora Pro and Outlook can be configured to use POP. Webmail and Traveler, on the other hand, always use IMAP (see above).
This description of POP has only touched on the most fundamental aspects of this email protocol. In actuality, POP can be configured to store its mail on the server. However, there are several considerations that must be taken into account when using this option. Therefore, other POP options are recommended only for advanced users and will not be discussed further in this document.
