IMAPPOP3

IMAP (Internet Message Access Protocol) and POP3 (Post Office Protocol version 3) are email retrieval protocols used by clients to access messages stored on a mail server. They are widely supported, but they work differently in how they store and synchronize messages.

IMAP keeps messages on the server and synchronizes state across multiple devices. Users can organize mail into folders, apply flags (such as read or replied), and perform server-side searches. Changes made by one client are reflected on others, making IMAP well suited to accessing mail from several devices.

POP3 is a simpler, download-oriented protocol. By default, it downloads messages to the client and may delete them from the server, though many servers offer an option to retain copies. This makes offline access straightforward and reduces server-side state, but it can complicate synchronization when accessing the same mailbox from multiple devices.

Security for both protocols is typically provided via TLS or SSL. IMAP commonly uses port 993 for encrypted connections and POP3 uses port 995, with STARTTLS available on some configurations for both. Authentication generally involves a username and password, though modern deployments may support OAuth 2.0.

IMAP was developed to support server-side storage and multi-device access and is defined in RFC 3501 (IMAP4rev1). POP3, defined in RFC 1939, emphasizes simplicity and offline retrieval. In practice, IMAP is preferred when users need consistent access across devices, while POP3 remains suitable for simple, local download workflows or limited server storage.

Both protocols are compatible with contemporary mail servers and clients, and many servers offer both options to accommodate different user needs.