- Require TLS and authenticated submission.
- Make sure the server is not an open relay.
- Publish SPF, DKIM and DMARC for the domain.
Port 58: XNS Mail
Port 58 is assigned by IANA to xns-mail (XNS Mail).
58
How xns-mail works
EmailMail servers hand messages to each other over port 58, 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
- Well-known (0-1023)
- Category
Is port 58 dangerous?
We have no specific security note for port 58. Its risk depends on the program actually listening on it. General advice for email services:
IANA registry entries for port 58
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| xns-mail | 58 | TCP, UDP | XNS Mail | - | - |
// source: IANA service name and port number registry
Which program uses port 58, and is it reachable?
Linux
sudo ss -ltnup 'sport = :58' # process listening on 58
sudo lsof -nP -i :58macOS
sudo lsof -nP -i :58
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 58 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 58 netstat -ano | findstr :58
From another machine
nmap -p 58 -sV <host> sudo nmap -sU -p 58 <host> nc -zv <host> 58
Block it in the firewall
sudo ufw deny 58/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 58" -Direction Inbound -LocalPort 58 -Protocol TCP -Action Block # Windows
What is port 58 used for?
Port 58 is assigned by IANA to xns-mail (XNS Mail).
Is port 58 TCP or UDP?
Port 58 is registered for TCP and UDP.
Is it safe to open port 58?
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 58 is open?
On Linux run "ss -ltnup 'sport = :58'", on macOS "lsof -nP -i :58", and on Windows "netstat -ano | findstr :58" to see the local process. From another machine, "nmap -p 58 <host>" shows whether it is reachable.