Quick Summary
IMAP (Internet Message Access Protocol) keeps emails on the server, enabling access from multiple devices.
IMAP (Internet Message Access Protocol) is an email retrieval protocol that manages emails directly on the server. Developed in 1986, it forms the foundation of modern multi-device email usage.
IMAP vs POP3
While POP3 downloads and deletes emails from the server, IMAP keeps them on the server. This allows you to access the same inbox from multiple devices such as smartphones, tablets, and computers.
IMAP Features
Server-side storage: Emails remain on the server.
Folder synchronization: Same folder structure across all devices.
Read status: Messages read on one device appear read on others.
Search: Server-side email search support.
IMAP Port Numbers
143: Standard IMAP port.
993: SSL/TLS encrypted IMAP (IMAPS).
ONS Mail and IMAP
ONS Mail fully supports the IMAP4rev1 standard and uses IMAPS (port 993) for secure connections.