Here we will cover the main differences between IMAP and POP3 for connecting an email account to email clients and look into common reasons for using either option.
There are pros and cons to using either IMAP or POP3, and the selection will differ based on how the email account will be used.
It is highly recommended to use either IMAP or POP3 for a specific email account. There shouldn't be a combination of both configurations being used at the same time for the same account. This can result in emails becoming "desynced" and missing on some devices.
This article briefly touches on SMTP as well.
Related Articles
Using Webmail vs. Email Client
Transfer Email from Previous Host Using Thunderbird
Set Up Mail Client Using Automatic Configuration Script
IMAP
When you connect over IMAP (Internet Message Access Protocol), the emails are saved on the server and any changes you make to them are synced to the server. For example, if you move an email to another folder, you'll find it moved on every device you check your email with.
Any changes made to emails will sync with all devices connected to that email address.
IMAP is best used if the email account will be added to multiple devices or multiple email clients. Most business owners prefer IMAP over POP3 since it allows more flexibility in checking email.
POP3
When you connect over POP3 (Post Office Protocol Version 3), the emails are downloaded and saved to your device.
By default, they are deleted from the server when they are downloaded. However, most email clients have a setting to save a copy on the server.
Any changes you make will only take place on the device that they're made on. For example, if you move an email into a different folder, it will only show in the new folder on the email client you moved it on.
POP3 is best used if the email account will only be checked from a single device and a single email client. It is also the best option if email account storage space on the server is a concern.
POP3 should not be used if the email account will be checked from multiple devices or multiple email clients.
It is strongly recommended to create a backup of emails if POP3 is used, as there is no way to retrieve them from the server if they are lost.
SMTP
SMTP (Simple Mail Transfer Protocol) is a standard protocol used for sending email messages between servers on the internet. Essentially, it's the language email servers use to communicate with each other when delivering emails.