One of the most common questions that come up in the course of my day is whether to choose IMAP or POP3 when setting up an email client. This decision comes up any time a person gets a new phone, tablet, desktop, or laptop on which they would like to receive email. I will briefly what exactly IMAP and POP3 means, the difference between the two, and how to decide which is the right choice for you.
IMAP and POP3 are electronic mail protocols. You can think of a protocol as a language that two computers can talk back and forth using. Both IMAP and POP3 have their own set of words and meanings that can be used when communicating between any email server and email client that support the protocols. When referring to the email server, we are only concerned with receiving mail and not with sending mail in this case.
The Internet Message Access Protocol, or IMAP protocol is the newer of the two email protocols in question. IMAP allows multiple simultaneous persistent connections to an email account, allowing more than one device to be connected and monitoring an inbox at one time. When a new email is delivered to a user’s mailbox, the message stays on the server and a local copy is temporarily stored on the user’s computer. This allows management of an email account mailbox that will stay synchronized with other email clients on other devices.
When messages are sent, received, deleted, or labelled by an email client using IMAP, the messages are uploaded and stored on the server. This can quickly lead to excessively large mailbox storage space, and large disk space usage charges from the email provider. Additionally, the larger the mailbox, the more resources are required by the server when working with the mailbox, potentially causing slower response times for all users on that server.
Post Office Protocol, or POP3 is an older email transfer protocol which operates differently than IMAP. When an email client using POP3 logs into a mail server to check the mailbox, only one connection is allowed at a time. POP3 typically downloads an email message to your local device and deletes the message from the email server. An option is available in any email client using POP3 to leave a copy of a message on the server for a set amount of time. Typically 7-10 days is sufficient. This allows other devices to retrieve a copy of the message as well, so you can have the same message on your phone, laptop, desktop, and tablet device. Sent and deleted messages are not stored on the server when using POP3, which drastically reduces the storage and resources used by the mailbox. Using POP3 typically avoids disk space usage charges, except for in extremely high mail volume cases.
The disadvantage of POP3 compared to IMAP is primarily in the management options. An email sent from a Smart Phone will not show up as a sent message on a user’s other devices when using POP3. A message deleted from a local device, such as a laptop, will not be deleted from other devices at the same time.
When configuring a device to retrieve email, you will want to use the same protocol on all of your devices. For example, if you use POP3 on your laptop, you will want to set up your phone and desktop email clients to use POP3 as well. Using multiple protocols to check the same email mailbox can cause inconsistencies in the inbox and possible corruption of email. Many times a user will set up an email client on a new device and find that they are receiving mail on one device, but not on their other devices. This is typically caused by using IMAP on one or more devices, and POP3 on other devices that all check the same mailbox.
We took a brief look at what a protocol is, as well as the two most popular email protocols in use today. A few advantages and disadvantages of both IMAP and POP3 were presented, as well as a brief description of how each works. We looked at a few of the issues that can rise when using both protocols to check the same email inbox, and why it is important to be consistent in our choice of which email protocol to use when checking our mail. I hope this explanation helps the next time you are setting up a new email client on any of your internet connected devices.