Port 143: IMAP
Read and manage email on the server.
- Port
- 143
- Protocol
- TCP
- Service
- IMAP
- Exposure
- Expose only with access controls
What is port 143 used for?
Mail clients that keep mail on the server.
Is it safe to expose port 143 to the internet?
Prefer IMAPS on 993 or STARTTLS, so credentials are encrypted.
If port 143 seems closed or unreachable
- Check that the IMAP service is running and listening on port 143, not only on 127.0.0.1.
- Check the firewall on the host itself (Windows Defender Firewall, iptables, nftables, ufw) for a rule that allows TCP 143.
- If the host is behind a router, confirm the forwarding rule points to the correct internal address and that your internet provider does not use carrier-grade NAT.
- Test from outside your own network. A port can be open locally and blocked at the edge, or the other way round.
Using port 143 safely
Port 143 can be exposed when the host exists to provide this service, but add controls: restrict source addresses where you can, require strong authentication and encryption, and monitor the logs for repeated failures.
Check whether port 143 is open on your host
The check connects from our server, so it shows what the internet can reach.
Open the port checker