Is port 504 (Citadel) dangerous?

Port 504 is classified as medium risk. It is commonly exposed but consider using encrypted alternatives where available and monitor activity.

Should port 504 be open on my firewall?

Port 504 can be open but should be monitored closely. Keep the service updated and prefer encrypted alternatives where available.

Port 504 (Citadel) uses the TCP transport protocol and falls under the Messaging category.

:504 (TCP)

Medium Risk

TCP — Messaging

Port Number 504

Service Name Citadel

Transport Protocol TCP

Category Messaging

Security Risk Medium

Port Range Well-Known (0-1023)

Port 504 is assigned to Citadel, an open-source groupware and messaging server providing email, calendaring, and bulletin board services.

TCP Messaging

Port 504 (Citadel) is classified as medium risk. While this service is commonly exposed, consider using encrypted alternatives where available.

Recommendation: Keep the service updated. Monitor logs for unusual activity.