- Require TLS and authenticated submission.
- Make sure the server is not an open relay.
- Publish SPF, DKIM and DMARC for the domain.
Port 1556: VERITAS Private Branch Exchange
Port 1556 is assigned by IANA to veritas_pbx (VERITAS Private Branch Exchange), veritas-pbx (VERITAS Private Branch Exchange IANA assigned this well-formed service name as a replacement for "veritas_pbx".).
1556
How veritas_pbx works
EmailMail servers hand messages to each other over port 1556, 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
- Assigned2 registered services
- Range
- Registered (1024-49151)
- Category
Is port 1556 dangerous?
We have no specific security note for port 1556. Its risk depends on the program actually listening on it. General advice for email services:
IANA registry entries for port 1556
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| veritas_pbx | 1556 | TCP, UDP | VERITAS Private Branch Exchange | - | 2004-04 |
| veritas-pbx | 1556 | TCP, UDP | VERITAS Private Branch Exchange IANA assigned this well-formed service name as a replacement for "veritas_pbx". | - | 2004-04 |
// source: IANA service name and port number registry
Which program uses port 1556, and is it reachable?
Linux
sudo ss -ltnup 'sport = :1556' # process listening on 1556
sudo lsof -nP -i :1556macOS
sudo lsof -nP -i :1556
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1556 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 1556 netstat -ano | findstr :1556
From another machine
nmap -p 1556 -sV <host> sudo nmap -sU -p 1556 <host> nc -zv <host> 1556
Block it in the firewall
sudo ufw deny 1556/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 1556" -Direction Inbound -LocalPort 1556 -Protocol TCP -Action Block # Windows
What is port 1556 used for?
Port 1556 is assigned by IANA to veritas_pbx (VERITAS Private Branch Exchange), veritas-pbx (VERITAS Private Branch Exchange IANA assigned this well-formed service name as a replacement for "veritas_pbx".).
Is port 1556 TCP or UDP?
Port 1556 is registered for TCP and UDP.
Is it safe to open port 1556?
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 1556 is open?
On Linux run "ss -ltnup 'sport = :1556'", on macOS "lsof -nP -i :1556", and on Windows "netstat -ano | findstr :1556" to see the local process. From another machine, "nmap -p 1556 <host>" shows whether it is reachable.