What is port 993 used for?

Port 993 is the standard TCP port used for IMAPS (Secure Mail Retrieval). It is commonly used by Dovecot, Courier-IMAP, Cyrus IMAP. Secure Internet Message Access Protocol over TLS for downloading and synchronizing email folders across devices.

How do I check if port 993 is open?

Enter your public IP or hostname into the scanner tool and click Check. A sub-second raw TCP socket handshake will be initiated from our edge server to port 993 on your target. If the 3-way handshake finishes with SYN-ACK, the port is OPEN. If an RST packet is returned, the host is reachable but the port is CLOSED. If packets time out without response, the port is FILTERED by an ISP or firewall.

Is port 993 safe to expose to the public internet?

Port 993 is generally safe to expose when running standard, patched services with strong authentication. However, always ensure your software is updated and access control policies are strictly enforced.

Why does port 993 show as closed or filtered?

If port 993 reports CLOSED or FILTERED, confirm that: 1) Your service is actively running and bound to 0.0.0.0 (not just localhost/127.0.0.1); 2) Your router has a port forwarding rule directing external port 993 to your machine's local IP; 3) Your operating system firewall (Windows Defender Firewall, ufw, or iptables) allows incoming connections on port 993.