Port 143: IMAP
Port 143 is IMAP, which keeps mail on the server and syncs it across devices. The encrypted variant, IMAPS, uses port 993 and is what most clients use today.
TCPEmailUnencrypted by defaultIANA assigned
| Port number | 143 |
|---|---|
| Service | Internet Message Access Protocol |
| Protocol | TCP |
| Category | |
| Default encryption | No |
Security note. Port 143 is not encrypted by default. Restrict it to trusted networks, or use an encrypted alternative where one exists, to avoid exposing credentials and data in transit.
Frequently asked questions
What is port 143 used for?
Port 143 is IMAP, which keeps mail on the server and syncs it across devices. The encrypted variant, IMAPS, uses port 993 and is what most clients use today.
Is port 143 TCP or UDP?
Port 143 (IMAP) uses TCP.
Is port 143 secure?
Port 143 is not encrypted by default. Where possible, use an encrypted alternative or tunnel it over TLS or a VPN.
Should I open port 143 on my firewall?
Only if you specifically need IMAP. Expose it to the smallest set of trusted sources, and never open database or Windows-service ports to the whole internet.