- Require TLS and authenticated submission.
- Make sure the server is not an open relay.
- Publish SPF, DKIM and DMARC for the domain.
Port 4538: Software Data Exchange Gateway
Port 4538 is assigned by IANA to swx-gate (Software Data Exchange Gateway).
4538
How swx-gate works
EmailMail servers hand messages to each other over port 4538, 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 4538 dangerous?
We have no specific security note for port 4538. Its risk depends on the program actually listening on it. General advice for email services:
IANA registry entries for port 4538
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| swx-gate | 4538 | TCP, UDP | Software Data Exchange Gateway | - | 2006-05 |
// source: IANA service name and port number registry
Which program uses port 4538, and is it reachable?
Linux
sudo ss -ltnup 'sport = :4538' # process listening on 4538
sudo lsof -nP -i :4538macOS
sudo lsof -nP -i :4538
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 4538 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 4538 netstat -ano | findstr :4538
From another machine
nmap -p 4538 -sV <host> sudo nmap -sU -p 4538 <host> nc -zv <host> 4538
Block it in the firewall
sudo ufw deny 4538/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 4538" -Direction Inbound -LocalPort 4538 -Protocol TCP -Action Block # Windows
What is port 4538 used for?
Port 4538 is assigned by IANA to swx-gate (Software Data Exchange Gateway).
Is port 4538 TCP or UDP?
Port 4538 is registered for TCP and UDP.
Is it safe to open port 4538?
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 4538 is open?
On Linux run "ss -ltnup 'sport = :4538'", on macOS "lsof -nP -i :4538", and on Windows "netstat -ano | findstr :4538" to see the local process. From another machine, "nmap -p 4538 <host>" shows whether it is reachable.