When you configure your email account in an email client, you must choose the type of protocol you will use. Currently, the two protocols that email managers allow you to choose from are IMAP and POP3.
The main difference between these two protocols is that IMAP stores messages on the mail server while POP3 downloads and stores them locally.
1.-IMAP
This protocol works directly on the mail server. To check email, it connects to the server and displays the existing content. When an email is received, it is stored on the server and is accessible from any other device that checks the email.
Current email managers have options so that emails are also stored locally using this protocol.
Advantages:
Email is accessible from any device with Internet access.
Since it works directly with the mail server, any changes are visible from all devices accessing the account.
If the device used to access the account has a failure, emails are not lost because they are stored directly on the server.
Disadvantages:
Since email is stored on the server, it is easier to fill up the mailbox capacity.
If IMAP folders are created, they are not accessible from POP3 configurations.
2.-POP3
An email client configured as POP3 connects to the server and downloads emails to the local device. Once this is done, it deletes the downloaded messages from the server, making them available only locally. With this protocol, sent messages are only available locally.
Current email managers allow the option of keeping a copy of downloaded messages on the server, or specifying that only messages older than a certain age should be deleted.
Advantages:
You can keep a local email history without needing an Internet connection.
The mail server space does not fill up because once the email is downloaded, it is deleted from the server.
Disadvantages:
Sent emails are only accessible locally.
Emails cannot be viewed from different devices.
It consumes local storage space.
If the device suffers a failure, emails may be lost and become inaccessible.