Glossary · Email

IMAP (Internet Message Access Protocol)

IMAP is a protocol that lets email clients read and manage messages stored on a server, keeping folders and read state in sync across all your devices.

Updated October 6, 2026

IMAP (Internet Message Access Protocol) is a protocol for accessing email that stays on the mail server. The client displays and organises messages remotely, so the mailbox looks the same on every device.

Why it matters

Because the server holds the master copy, reading, flagging, moving or deleting a message on your phone is reflected on your laptop. This is why IMAP replaced POP3 for most people who use more than one device. It also means mailbox size is limited by the server quota, and a slow or unreachable IMAP server makes mail appear to vanish even though nothing was lost.

Example

Typical client settings for a hosted mailbox:

Incoming (IMAP): imap.example.com
Port: 993  Security: SSL/TLS
Outgoing (SMTP): smtp.example.com
Port: 587  Security: STARTTLS
Username: jane@example.com

Port 143 is the unencrypted default (usually upgraded with STARTTLS) and 993 is IMAP over TLS.

Common mistakes

  • Configuring IMAP for incoming mail but forgetting that sending needs separate SMTP settings.
  • Using port 143 with no encryption, exposing the password.
  • Treating IMAP as a backup. If a message is deleted on one device, it is deleted for all of them.

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