IMAP stands for Internet Message Access Protocol and POP stands for Post Office Protocol.? Both of these protocols are used for email retrieval purposes ? specifically, they process the transfer of email messages from the server to an email client.

The POP email Retrieval Process

When you click the ?receive? option in your email client, it will connect to your remote email server. It will retrieve all mail and store it locally as new mail, and it will also it will delete those emails from the server.? The exception to this is if the email client is configured to “keep mail on server”, in which case the client will just disconnect.

The IMAP email Retrieval Process

The IMAP protocol operates differently.? First, when you click the ?receive? option, the email will connect to the remote email server. It then pulls the user-requested content and caches it locally. Then it will process user edit processes, such marking emails as read or deleting emails and so on.? Finally it disconnects from the server.

IMAP vs POP3 ? What’s the Difference?

The two protocols generally operate on different ports.? An IMAP server commonly utilizes port 143, and IMAP-over-SSL utilizes port number 993, whereas a POP server utilizes port 110 and POP-over-SSL utilizes port 995.

Essentially, POP is a one-way communication path, whereas IMAP offers two-way synchronization between server and client.? POP is sufficient if you?re accessing your email using only one device such as your PC.? It downloads copies of emails for offline reading, and deletes those emails from the remote server (although in modern email clients, there are options to leave POP emails on the server for a certain amount of time before deletion).

IMAP is the protocol of choice if you need to access your email from multiple locations ? for example, both your office workstation and your notebook or tablet. IMAP will sync webmail between your mobile device and your workstation. IMAP keeps emails on the server until you erase them manually. Additionally, while using IMAP, if you delete email from a single device, you?ll also delete the email from the server as well as other devices.

IMAP vs POP ? the Pros and Cons

The Advantages of POP

POP will download emails without leaving copies of them on the server.? This keeps the space used on the email server low. The other advantage is that mails are stored locally and are always accessible even without an internet connection. A connection will only be needed when sending and receiving email.? Additionally, it will offer you an option to leave copies of emails on the server, if you wish.

The Disadvantages of POP

Since there is no remote server copy, if? data is lost from the location where the email are downloaded, no email recovery option will be available and all your email will be gone unless you have regularly backed up your local email storage.

If you intend to use a single email account configured with POP, but want to use multiple email clients on multiple devices, some emails will be missed, since there is no synchronization between server and the devices/clients.

The Advantages of IMAP

IMAP is often preferred in many use-cases.? In the IMAP protocol, emails are stored on the remote server and are therefore accessible from multiple different locations. This saves local storage space on your devices. If you do wish to store mail locally, email clients can be configured accordingly. The size of your email message archive is determined only by your account?s server space, but not your personal device storage.

IMAP can take a little time to download and synchronize emails from some remote servers, but it?s a flexible, more reliable, and more complete email retrieval method compared to POP.


Using Outlook for POP or IMAP


Choose IMAP if you require the following:

(1)??? Access to your emails, both old and new, at multiple locations.

(2)??? Emails kept on the server rather than stored offline in your personal storage ? perhaps due to limited personal storage space on your device

(3)??? Real time email synchronization across all of your devices and the server.


Choose POP3 if you need:

(1)??? To access your email from a single location.

(2)??? Webmail for when you need to check new email remotely.

(3)??? To have your own regular backups of your email messages.

(4)??? Constant access to your email, regardless of internet availability.

(5)??? To minimize use of? storage space your server, perhaps due to a quota-based limitation.


Changing Microsoft Outlook Settings to Keep Emails on the Server While Using POP

This can be done when you first configure your email client the first time, or by editing settings later. In this demonstration, we have already configured the email server in Microsoft Outlook 2013 -? so we just need to edit Account Settings to change email storage on the server.


Email Account Settings


In the screenshot below, we need to double click on the email highlighted in the E-mail tab:


Select Email Account in Outlook



It is for a POP account.? Click on ?More Settings?.

Defining a POP3 Account


Then navigate to ?the ?Advanced? tab.? In the delivery section, tick ??Leave a copy of message on the server? and select your desired length of time.


Defining Advanced POP3 Parameters


However, if you choose a large time frame, your server Inbox may fill with emails, which could push you towards your storage quota.? If your server inbox reaches its maximum storage quota, any further emails you receive will bounce and you won?t receive new mail until you manually delete emails and free up some space on the server.? IMAP will also cause the same issue if you have limited server-side inbox space. In such a scenario, POP is your best choice, with the “Keep mail on server” option de-selected.


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