Port 993: IMAPS
TCP 993 is the port for IMAP over TLS. Fine on mail servers.
| Service | IMAP over TLS |
|---|---|
| Protocol | TCP |
| Exposure risk | Low: normally safe to expose |
| Range | Well-known (0–1023): binding needs root/admin on Unix |
What port 993 does
The standard port for mail clients reading mail securely (imap.gmail.com:993, outlook.office365.com:993).
Should port 993 be open?
Fine on mail servers.
Find what's listening on port 993
- Linux:
sudo ss -tulpn | grep :993 - macOS:
sudo lsof -nP -i :993 - Windows:
netstat -ano | findstr :993, then look up the PID in Task Manager.
Open or block it in a firewall
- ufw:
sudo ufw allow 993/tcp(ordeny) - firewalld:
sudo firewall-cmd --add-port=993/tcp --permanent && sudo firewall-cmd --reload - Windows:
New-NetFirewallRule -DisplayName "Port 993" -Direction Inbound -Protocol TCP -LocalPort 993 -Action Allow
Port assignment per the IANA Service Name and Transport Protocol Port Number Registry. Test several ports at once with the port scanner, or any port with the open port checker.
Questions about port 993
What is port 993 used for?
IMAP over TLS. The standard port for mail clients reading mail securely (imap.gmail.com:993, outlook.office365.com:993).
Is port 993 TCP or UDP?
TCP. IMAPS uses TCP port 993.
Is it safe to open port 993?
Low: normally safe to expose. Fine on mail servers.
How do I check if port 993 is open?
Use the checker on this page: it connects to your host on TCP 993 from the internet. Locally, run
nc -vz host 993 (macOS/Linux) or Test-NetConnection host -Port 993 (PowerShell). To see what is listening on your own machine, run ss -tulpn | grep :993 (Linux) or netstat -ano | findstr :993 (Windows).