- Require TLS and authenticated submission.
- Make sure the server is not an open relay.
- Publish SPF, DKIM and DMARC for the domain.
Port 3436: GuardControl Exchange Protocol
Port 3436 is assigned by IANA to gc-config (GuardControl Exchange Protocol).
3436
How gc-config works
EmailMail servers hand messages to each other over port 3436, one hop at a time, until the recipient's server.
- Transport
- TCP · UDP
- Exposure risk
- not rated depends on the program listening
- Encryption
- Unknownnot stated by the registry
- IANA status
- Assigned1 registered service
- Range
- Registered (1024-49151)
- Category
Is port 3436 dangerous?
We have no specific security note for port 3436. Its risk depends on the program actually listening on it. General advice for email services:
IANA registry entries for port 3436
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| gc-config | 3436 | TCP, UDP | GuardControl Exchange Protocol | - | 2002-03 |
// source: IANA service name and port number registry
Which program uses port 3436, and is it reachable?
Linux
sudo ss -ltnup 'sport = :3436' # process listening on 3436
sudo lsof -nP -i :3436macOS
sudo lsof -nP -i :3436
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3436 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 3436 netstat -ano | findstr :3436
From another machine
nmap -p 3436 -sV <host> sudo nmap -sU -p 3436 <host> nc -zv <host> 3436
Block it in the firewall
sudo ufw deny 3436/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 3436" -Direction Inbound -LocalPort 3436 -Protocol TCP -Action Block # Windows
What is port 3436 used for?
Port 3436 is assigned by IANA to gc-config (GuardControl Exchange Protocol).
Is port 3436 TCP or UDP?
Port 3436 is registered for TCP and UDP.
Is it safe to open port 3436?
It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Require TLS and authenticated submission.
How do I check if port 3436 is open?
On Linux run "ss -ltnup 'sport = :3436'", on macOS "lsof -nP -i :3436", and on Windows "netstat -ano | findstr :3436" to see the local process. From another machine, "nmap -p 3436 <host>" shows whether it is reachable.