POP vs. IMAP

Comparison of Services

POP and IMAP are two different e-mail protocols (standards) which allow e-mail programs on a user's computer to communicate with centralized e-mail servers to receive e-mail. E-mail programs such as Outlook, Thunderbird, Eudora, Mac Mail and Entourage allow use of either the POP or IMAP protocols. (Web-based programs access e-mail directly from the centralized servers rather than using the IMAP or POP protocols to copy mail to the user's computer. Lotus Notes uses a proprietary protocol to access mail from the server.) SF State encourages the use of the IMAP protocol for accessing SF State e-mail. Previously, SF State recommended POP; however, the newer and more efficient IMAP protocol is now recommended.

The following information is provided to help clarify the differences between POP and IMAP service at SF State.

POP vs IMAP
POP	IMAP
By default, downloads messages to your computer and then deletes them from the mail server	Generally leaves messages on the server until the user explicitly deletes them
Can use local folders
Allows off-line e-mail viewing and composing
E-mail is accessible on only one computer¹	Consistant view of e-mail from any computer
E-mail is delivered every 10 minutes	E-mail is delivered without delay²
E-mail can be left on the server for a maximum of 10 days	E-mail can be left on the server indefinately ³
You must back up your e-mail	E-mail is backed-up automatically

While it is technically possible to use POP to access e-mail from more than one computer, the Internet Official Protocol Standard (RFC 1939) suggests that POP is intended to be used when messages are downloaded and then deleted from the server (making them unavailable from other computers).
E-mail delivery is dependent on server mail volume. E-mail messages are delivered from a mail queue on a first come, first served basis. Excessive e-mail server volume can cause delivery delays for both POP and IMAP recipients.
E-mail can be left on the server as long as the storage quota is not exceeded. (Old or less frequently accessed messages can be moved from the server to local folders for continued access while reducing e-mail file size on the server.)

For step by step instructions on changing from POP to IMAP, refer to the installation and configuration guide for your e-mail program. If you wish to transfer your mail and contacts from your computer to the e-mail servers as part of your switch to IMAP, contact the DoIT Help Desk (x81420) for e-mail program eligibility and assistance.

Configuration Settings for POP

While IMAP is the campus recommended protocol, if you prefer POP or your college IT staff recommends you use POP, use the following configuration settings:

POP Account: your e-mail address
POP Server: you can find your server by logging in at http://www.sfsu.edu/email
Incoming Server Port Numbers: (POP3) 110, Outgoing Server (SMTP): 25
Under Account Settings (Advanced Tab in Outlook) uncheck the box which refers to "Leaving mail/copy of messages on Server"
- Alternatively, if you do wish to leave mail on the server, check the box to leave mail on the server, but also check the box that references "Deleting or Removing mail from server after ____ days" and enter a number less than or equal to 10 in the blank.

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Last Modified: 28 March 2008
doit@sfsu.edu