All ports
Port50/UDP
re-mail-ckPort
50
Protocol
UDP
Category
Well-Known
Service
re-mail-ck
What is port 50?
Port 50/UDP is a Well-Known port, assigned by IANA for widely recognized services. It is associated with the re-mail-ck service.
Remote Mail Checking Protocol
Useful commands
nmapnmap -p 50 -sV example.comnetcatnc -zv example.com 50curlcurl -v http://example.com:50/telnettelnet example.com 50bash(echo > /dev/udp/example.com/50) 2>/dev/nullFirewall commands
UFWAllow
sudo ufw allow 50/udpDeny
sudo ufw deny 50/udpiptablesAllow
sudo iptables -A INPUT -p udp --dport 50 -j ACCEPTDeny
sudo iptables -D INPUT -p udp --dport 50 -j ACCEPTfirewalldAllow
sudo firewall-cmd --permanent --add-port=50/udpWindowsAllow
netsh advfirewall firewall add rule name="Open Port 50" dir=in action=allow protocol=UDP localport=50Security Risks
- Open relay used for spam
- Email spoofing
- Brute force attacks against email accounts
- Information disclosure in email headers
Frequently Asked Questions
What service runs on port 50/UDP?
Port 50/UDP is associated with the re-mail-ck service. Remote Mail Checking Protocol
Is it safe to expose port 50 to the Internet?
It depends on the service and configuration. Port 50 (re-mail-ck) is a Well-Known port. If you need to expose it, keep the service updated, use strong authentication, and configure a firewall. It's always recommended to restrict access by IP when possible.
How do I check if port 50 is open?
You can use nmap: `nmap -p 50 -sV example.com`, netcat: `nc -zv example.com 50`, or the bash command: `(echo > /dev/udp/example.com/50) 2>/dev/null && echo "Open" || echo "Closed"`.
How do I open or close port 50 on my firewall?
On Linux with UFW: `sudo ufw allow 50/udp` (open) or `sudo ufw deny 50/udp` (close). With iptables: `sudo iptables -A INPUT -p udp --dport 50 -j ACCEPT`. On Windows: `netsh advfirewall firewall add rule name="Open Port 50" dir=in action=allow protocol=UDP localport=50`.
What applications and services use port 50?
Port 50/UDP is used by the re-mail-ck service. Specific uses depend on the software and configuration. Check our related tools section for more information.