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IMAP vs. POP definitions

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IMAP vs. POP: Differences and Port Numbers to Use

IMAP and POP are two different modes in which email software clients can access and read email from the server.

In IMAP mode, your emails are viewed through the internet while remaining on the mail server. Changes made to messages and folders through a mail client in IMAP mode are implemented on the server. For example, if you delete an email from your office Outlook software and access your email again using your home Outlook software it will show the deletion you made from your office.

IMPORTANT: You should only manipulate folders (rename/add/delete) using the Webmail interface. Doing so from an email client using IMAP may cause folders to disappear from the Webmail interface (though the emails will still be on the server somewhere).

In POP mode, emails are downloaded from the mail server every time you check your mail. Changes made to messages and folders through a mail client in POP mode are implemented locally on your computer. For example, if you delete an email from your office Outlook software and access your email again from your home Outlook software, the message you previously deleted would reappear as it was not actually deleted from the server but only on your office computer.

IMPORTANT: Some email software clients using POP mode will download and DELETE emails from the server by default. If you decide to use POP, make sure you select the option to leave emails on the server before accessing your email.

In order to setup a POP account please follow all of the normal instructions available under each of the software clients. There are two points where the instructions differ:    

  • When initially creating the account you must designate POP or POP3 instead of IMAP.  
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  • When assigning the Port Number for Incoming Mail (cmail.chass.utoronto.ca) you use 995 instead of 993.

Email Backup Tips

  • When using POP to retrieve your email be sure to leave a copy of the message on the server. There is a significant risk of losing email with POP if the email is deleted from the server and a local copy is placed on your computer. If anything should thereafter happen to your computer, your messages may be lost permanently. If you do choose this method, we strongly recommend you make regular backups of your email -- preferably to an external hard drive.
  • While IMAP can be convenient for accessing email from multiple computers, all your email still resides on the server which means you will not be able to access your email in "offline" mode. One solution to this would be to setup another profile within your email client that uses POP mode and periodically login to this profile and "synchronize" your emails. Again, be sure to select the leave mail on the server option. Another solution would be to create a local folder within your email client and copy and paste the mail content into this folder whenever you would like a backup of it.

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Last update: 2010-03-16 00:13
Author: CP
Revision: 1.10