This guide details the differences between the IMAP and POP3 protocols on an email software/client (Outlook, Microsoft 365, Thunderbird, Apple Mail, eM Client, etc.) and explains why it is crucial not to use them simultaneously for the same email address managed by Infomaniak.

IMAP (recommended)

IMAP is the synchronization protocol. Messages remain on the server and can be accessed from anywhere.

• Multi-device access: your emails are synchronized between your computer, your smartphone and the Webmail Infomaniak.
• Collaborative work: ideal for shared mailboxes. If a user moves or deletes a message, the change is visible to everyone.
• Security: in case of a computer failure, your messages remain saved on the server.

POP3 (specific use)

POP3 is a download protocol. Messages are retrieved on your computer and usually deleted from the server.

• Offline consultation: messages are stored locally on your hard drive.
• Major drawback: once downloaded, messages are no longer visible on the Webmail or on your other devices.
• Risks: if you use the option "keep a copy of messages on the server", you risk duplicate downloads and synchronization errors.

Important: never mix POP and IMAP

Simultaneous use of these two protocols for the same address causes major technical conflicts:

• Unexplained disappearance of messages on some devices.
• Repeated downloads of old messages already read (especially on Outlook).
• Unnecessary saturation of storage space.

Tip: favor the use of IMAP on all your email software.

Refer to these other guides to configure an IMAP account or to switch from POP to IMAP.