- Port
- 143
- Protocol used by the service
- TCP
- Encryption
- Unencrypted
- IANA description
- Internet Message Access Protocol
- IANA service name
- imap
Note: IANA also lists other, unrelated entries for port 143 on a different protocol — 143/udp — Reserved. This is not part of IMAP itself.
What port 143 is used for
End-user email retrieval with server-side folder state, letting multiple devices see the same mailbox in sync — the model most modern mail clients use by default.
Is port 143 encrypted?
Not encrypted by default on this port; the encrypted variant (IMAPS) runs on port 993 instead, which most modern mail clients use automatically.
Firewall & exposure considerations
Should generally use the encrypted variant (993) rather than plain 143 for anything beyond legacy compatibility, especially for mail accessed outside a trusted network.
Related ports
References
Look up any other port
Search the full IANA registry — all 6,100+ ports and 12,500+ protocol-specific records — on the Port Lookup tool.
Last reviewed: . Data source: IANA Service Name and Transport Protocol Port Number Registry. Security and usage notes are this site's own editorial content, not official IANA data.