Understand the difference between POP3 and IMAP

This guide explains the differences between IMAP and POP3 email protocols from an email software/client (Outlook, Microsoft 365, Thunderbird, Apple Mail, eM Client, etc.) and why you should never use them simultaneously with (in particular) an email address managed by Infomaniak.

Advantages of IMAP / IMAP4

With IMAP, emails remain on the server and are accessible from any computer connected to the internet, via Mail, Infomaniak's email interface, or Infomaniak Mail, the mobile app.

This is useful if your connection is permanent, if you want to access all your messages from multiple locations simultaneously (at home, on the go, while traveling, etc.), and if multiple users share a service mailbox from different workstations.

You will always have the same view of the messages on the server; everyone will see the same messages: if a message is deleted by one user, the other users will no longer see that message. If it is moved to a folder on the server, all users will see that message in that folder.

Disadvantages

You generally need to be connected to the internet to view messages (but some email software/clients and certain mobile devices will allow you to view the inbox even without a 4G/5G or WiFi connection).

Advantages of POP/POP3

Emails are removed from the server and downloaded to the computer. They are therefore accessible even offline. Useful if your connection is costly or non-permanent, or if you want to keep a local copy if you stop your subscription to the email provider.

Disadvantages

Emails no longer appear on Mail. You cannot have multiple people accessing the same mailbox because messages are deleted after each access, which can lead to missing or disappearing messages. Additionally, if you "keep a copy of messages on the server" (an option in the email software/client), the more emails kept in duplicate, the greater the risk of encountering issues (see below).

Never mix POP and IMAP

It can happen that your email software/client, particularly Microsoft Outlook, starts retrieving all messages, including those you have already received and read in the past.

The cause is often a POP3 incoming server configuration with the "keep a copy of messages on the server" option.

This configuration may work perfectly for a while, then problems can arise, such as re-downloading messages.

To avoid this, it is recommended to use the IMAP protocol: this guide explains how to set up an IMAP account, and this guide provides solutions for changing an existing account from POP to IMAP.

If you still want to use the POP3 protocol avoid enabling the option to keep a copy of messages on the server.