Email: SSL POP3 vs. SSL IMAP - Advantages

Email clients (the programs you run on your own computer to read email) commonly provide two different protocols for getting email: SSL IMAP and SSL POP3.

We ensure email security by supporting "Secure Socket Layer" (SSL) for our Webmail, POP, IMAP and SMTP servers.

If you need to send or receive email before completing configuration of your local email client, you can still access email through your web browser interface via Outlook Web Access (OWA):

Can't figure out which one to use? Read on.


SSL IMAP is the Secure Socket Layer Internet Message Access Protocol, or as it was once known, the Interactive Mail Access Protocol. It represents a communications mechanism for mail clients to interact with mail servers, and manipulate mailboxes. Users ordinarily view email messages directly on the server.

Below are advantages and disadvantages of using SSL IMAP.


  • With SSL IMAP, your mail stays on the email server: Since the messages are retained on the server, SSL IMAP allows users to connect from a variety of machines. You can organize your mail into folders, and all the folders live on the server as well. This approach makes it extremely easy for you to access your email from any machine, and regardless of which machine you use, you have access to all of your mail in all of your folders.
  • Instant access to new messages: When connected to the internet, SSL IMAP allows users to access new messages instantly on their computers. For users with many or large messages, using SSL IMAP4 can result in much faster response times.
  • More efficient use of bandwidth: SSL IMAP does not download all the emails to your inbox but it streams the headers of each message to your inbox. Only the ones that you select for download will be sent to your inbox. The SSL IMAP4 protocol allows clients to separately retrieve portions of either individual parts or the entire message. These mechanisms allow clients to retrieve the text portion of a message without retrieving attached files or to stream content as its being fetched. Basically, you only download the messages you select.
  • Keeps track of message state (information to be kept on the server): Through the use of flags defined in the SSL IMAP4 protocol, clients can keep track of message state (e.g.: whether or not the message has been read, replied to or deleted). These flags are stored on the server, so multiple clients accessing the same mailbox at different times can detect state changes made by other clients.


  • Your email box may fill up: Because all your emails reside on the server, your "email box" (the space on the server allocated for your emails) may fill up. ** Learn to manage your emails.
  • You cannot view your emails without an active internet connection: Although when disconnected, most email clients have some way to cache email on the local machine, but it really depends on the type of email program that you use because not all email client programs have the option to leave a copy on the local computer.

Instructions for setting up a number of popular clients:

Email: Set-Up Guides and Account Information


SSL POP3 is the Secure Socket Layer Post Office Protocol 3, which perhaps is the most popular mail access protocol. It addresses remote mail access needs. Users ordinarily download their messages to a local machine, and the messages are deleted from the server. This is especially important on low-bandwidth connections.


  • Email box will not fill up: With SSL POP3, all your emails will be downloaded to your local computer. Therefore, your "email box" (the space on the server allocated for your emails) will not fill up.
  • Local copies of your email: SSL POP3 will download all your emails to your local computer, which will allow you to view your emails even when you’re not connected to the internet.
  • Good choice for dial-up connections: SSL POP3 is designed to allow end-users with intermittent connections such as dial-up connections to retrieve email when connected, and then to view and manipulate the retrieved messages without needing to stay connected.
  • Widely accepted mail protocol: SSL POP3 is a common protocol that is widely accepted with most email client programs, such as Outlook, Outlook Express, Entourage, Thunderbird, etc.


  • Your messages are not available from other locations: Since SSL POP3 downloads all your emails to your local computer, the emails that were residing on the server will be deleted. If you want to read your email both on your desktop machine and your laptop (depending on whether you are working in the office or on the road), SSL POP3 makes it difficult.
  • Less capable then SSL IMAP: SSL POP3 simply acts as an interface between the email client and the text file containing your messages. SSL POP3 generally connects, retrieves all messages, stores them on the user's PC as new messages, deletes them from the server, and then disconnects.

Instructions for setting up a number of popular clients:

Email: Set-Up Guides and Account Information


Cal Poly Pomona – I&IT eHelp - Email Account Information

Email: Cal Poly Pomona Email Basics

Wikipedia, The Free Encyclopedia – Internet Message Access Protocol

Wikipedia, The Free Encyclopedia – Post Office Protocol – How Email Works