Information Technology

POP vs. IMAP vs. Outlook Anywhere Comparison Matrix

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POP Protocol
IMAP Protocol
Native Exchange (Outlook Anywhere) Protocol
Pros and Cons

E-mail programs, such as Thunderbird, access e-mail from a server in one of two ways: POP (Post Office Protocol) or IMAP (Internet Message Access Protocol). Microsoft Outlook (PC or Mac), Entourage (Mac), Mail (Mac - 10.6 and newer) can access e-mail using POP, IMAP or Outlook Anywhere (formally known as MAPI or native Exchange). Each method offers different advantages to the user. With POP, e-mails are downloaded from a remote server to your local machine. While this method gives users offline access to previously downloaded e-mails, keeping track of e-mails requires use of the same workstation. IMAP and Outlook Anywhere offers greater mobility because e-mail and folders are stored on a remote server rather than your local machine. With IMAP or Outlook Anywhere you can access e-mail from any computer, from your residence across the Hudson River, to an Internet Café in Australia, as long as Internet or network access and an IMAP or Outlook Anywhere compatible e-mail program are available.

POP PROTOCOL

Accessibility
The Post Office Protocol (POP) mail protocol consists of a server and client. The server stores messages in a central location, and the client (such as Thunderbird or Mail) downloads messages to the user’s local machine. By default, most POP e-mail programs are set up to delete e-mail off the server once it is downloaded. That means that your local machine is the only place that your e-mail exists. If you need to read your mail from more than one location, you will need to set your e-mail client to leave e-mail on the server and delete it after a specified number of days (Note: Not all e-mail clients have the "leave mail on server for 'x' number of days" feature). However, you will not be able to view outgoing mail from another location unless you send a copy of the outgoing mail to yourself. If you want to keep track of all your e-mail from different computers, (i.e. home, office and laptop computers), POP is not the best e-mail solution.

Connectivity
Unlike IMAP or Outlook Anywhere, which requires constant connectivity to the network to access e-mail, POP e-mail can be handled offline; a connection is only needed to transfer e-mail between the server and your local machine when sending or retrieving mail. This results in shorter phone calls for dial-in users and no risk of being dropped while composing a message.

Message Management
When downloading messages with POP, you have little control over what messages are downloaded from the server. Although some e-mail programs, like Thunderbird, can be configured to avoid downloading messages larger than a specific size, and can even filter incoming e-mails and redistribute them into designated folders on your local machine, POP does not allow you to preview messages before downloading them. POP downloads any and all e-mails and attachments directly onto your machine. If you have POP configured to leave messages on the server, all e-mails and attachments will be downloaded again the next time you check your in-box from a different machine. This can be a real drag when you're on the road.

Calendar Access
POP clients allows you to store and access your Exchange calendar from within your client only and not available in Webmail or a smartphone device.

Contacts Access
POP clients allows you to store and access your Exchange contacts from within your client only and not available in Webmail or a smartphone device.

Storage
Normally, only the POP inbox resides on the server. When campus servers are backed up, only POP mail in this folder (e-mail that has not been downloaded and e-mail that has been left on the server) will be backed up centrally. Unless you back up the e-mail on your local machine daily, you could lose them if something happens to your computer. You can save all your e-mail onto floppies or other storage directly. Leaving mail on the server uses up disk quota space as e-mails and attachments begin to pile up. Deleting messages with a POP e-mail program, however, does not free up space on the server because only local copies are deleted. Set your program to remove e-mail from the server upon download to avoid disk quota problems.

Accessibility
The Internet Message Access Protocol (IMAP) is a more recently developed e-mail protocol that attempts to solve some of the problems raised by POP. Like POP, IMAP also consists of a mail server and client. However, IMAP differs from POP in that it assumes you will keep your e-mail on the server. All folders and messages exist on the server instead of your local machine. Because incoming e-mails are centrally located, you can access folders and messages from several different machines (i.e. home, office and laptop computers), each running an IMAP client program. From all of them you will see the same set of folders and messages. Your IMAP mail can be accessed from virtually any location with Internet access and is the best e-mail solution for users who need mobility.

Connectivity
Because IMAP-based e-mail programs keep everything on the e-mail server, IMAP requires constant connectivity to the server while you view or compose messages; this may not be the best solution if you are dialing in and paying by the minute. Some mail clients allow you to automatically save a local copy of your e-mails for offline viewing when you close out of the program. If you lose your network connection prior to exiting the program, you’ll have to reconnect to view the e-mails. Logging in with an IMAP e-mail client to check messages will take a little longer than POP (especially from a remote location) because the client must first contact the e-mail server and retrieve your preferences before using an IMAP setting.

Message Management
IMAP allows you to preview messages directly on the server and select the ones you want to view. With IMAP you can view e-mail information such as the subject line, sender and the size or name of e-mail attachments without having to download messages to your local machine. You can also create custom folders for your e-mails on the server to store and organize messages, like POP does on a local machine. Calendar Access
IMAP clients allows you to store and access your Exchange calendar from within your client only and not available in Webmail or a smartphone device.

Contacts Access
IMAP clients allows you to store and access your Exchange contacts from within your client only and not available in Webmail or a smartphone device.

Storage
Because IMAP keeps mail on the server until you delete it, you may run out of disk space if you save a lot of messages—especially if large files are attached to them. You must manually remove messages or save them to your local hard drive in order to clear up space on the server. Also because IMAP keeps mail on the server, a recent backup of your e-mail is always available since RU’s central computers are backed up on a regular basis.

E-mail Clients
Unlike with POP or IMAP, users can only use Outlook 2003/2007 or Entourage 2004/2008 e-mail clients to access the Outlook Anywhere protocol or using a web browser to access the Webmail interface.

Accessibility
The Outlook Anywhere (also known as MAPI or full Exchange) protocol that attempts to solve some of the problems raised by POP. Outlook Anywhere is exactly like the IMAP protocol with the added bonus of being able to sync and view your Exchange calendar and contacts on multiple computers/devices as long as all clients are configured to use the Outlook Anywhere / ActiveSync protocol. Like POP, Outlook Anywhere also consists of a mail server and client. However, Outlook Anywhere, like IMAP, differs from POP in that it assumes you will keep your e-mail on the server. All folders and messages exist on the server instead of your local machine. Because incoming e-mails are centrally located, you can access folders and messages from several different machines (i.e. home, office and laptop computers), each running an Outlook Anywhere client program - Outlook 2003/2007 or Entourage 2004/2008. From all of them you will see the same set of folders and messages. Your Outlook Anywhere mail can be accessed from virtually any location with Internet access and is the best e-mail solution for users who need mobility, including via a web browser (webmail).

Connectivity
Because Outlook Anywhere-based e-mail programs keep everything on the e-mail server, Outlook Anywhere requires constant connectivity to the server while you view or compose messages; this may not be the best solution if you are dialing in and paying by the minute. Some mail clients allow you to automatically save a local copy of your e-mails for offline viewing when you close out of the program. If you lose your network connection prior to exiting the program, you’ll have to reconnect to view the e-mails. Logging in with an Outlook Anywhere e-mail client to check messages will take a little longer than POP (especially from a remote location) because the client must first contact the e-mail server and retrieve your preferences.

Message Management
Outlook Anywhere clients allows you to store all your e-mail on the mail server. You can create custom folders for your e-mails on the server to store and organize messages, like POP does on a local machine.

Calendar Access
Outlook Anywhere clients allows you to store and access your Exchange calendar from within your client, Webmail or a smartphone device configured to use ActiveSync. If and when an entry is created or modified, the changes are pushed to all Outlook Anywhere clients within seconds.

Contacts Access
Outlook Anywhere clients allows you to store and access your Exchange contacts from within your client, Webmail or a smartphone device configured to use ActiveSync. If and when an entry is created or modified, the changes are pushed to all Outlook Anywhere clients within seconds.

Storage
Because Outlook Anywhere keeps mail on the server until you delete it, you may run out of disk space if you save a lot of messages—especially if large files are attached to them. You must manually remove messages or save them to your local hard drive in order to clear up space on the server. Also because Outlook Anywhere keeps mail on the server, a recent backup of your e-mail is always available since RU’s central computers are backed up on a regular basis.

Though POP, IMAP and Outlook Anywhere perform similar tasks, one may be more beneficial or effective than the other in certain situations. Which should you use? The table below compares the pros and cons of how POP, IMAP and Outlook Anywhere perform under similar conditions. Review it to examine which method best suits your needs.

* Entourage uses a protocol called WebDev to establish a full Exchange or Outlook Anywhere connection