Port 5766OpenMail NewMail Server

Port 5766 is assigned to the OpenMail NewMail Server, a service with no established public deployment details.

transport: tcp · udp
in transit: cleartext
assignment: official
risk: 1/10
lookups: 0

also known as openmailns

Technical Details

what runs on :5766

OpenMail NewMail Server is registered on port :5766 over tcp and udp to OpenMail Encyclopedi][Don Loughry. We don't have a technical write-up for it beyond the IANA registry entry.

In nmap's internet-wide scan data this port is never observed open, so if it's open on your network it's more likely a custom or misconfigured service than the registered one.

find what's listening on :5766

this machine

# linux
sudo ss -tulpn 'sport = :5766'

# macos / bsd
sudo lsof -nP -i :5766

# windows (then: tasklist /FI "PID eq <pid>")
netstat -ano | findstr :5766

another host

nmap -sV -p T:5766 <host>
sudo nmap -sU -sV -p U:5766 <host>

run it? the handshake, the implementations you meet in the wild and the flags that matter come from the engineers who do.

add technical details

Security Information

exposure of :5766

risk score

1/ 10safe

routine exposure. this port is rarely the way in on its own — keep it patched and logged and move on.

email averages 3.0 across 66 ports — this one sits 2.0 below.

in transit

cleartext

credentials and payloads are readable by anyone on path

assignment

official

registered with iana for this service — scanners fingerprint it by number

reachable over

tcp · udp

udp is connectionless — source addresses are trivially spoofed and it is a reflection favourite

security overview

no security notes recorded for :5766 yet

known exploits, hardening advice, what a compromise looks like — suggest an edit if you know its exposure.

Record

iana registry entry

port: :5766
service: OpenMail NewMail Server
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 1/10safe
category: Email
usage: IANA assigns TCP and UDP port 5766 to the OpenMail NewMail Server, registered to OpenMail Encyclopedi][Don Loughry. It has not appeared open in nmap's internet-wide scan data.
lookups: 0rank 993
added: 2026-10-09
updated: 2026-10-09
references: IANA service name registry — port 5766

Something wrong?

This record is maintained by the engineers who use port 5766. Every field on it is editable — change what's wrong, say how you know, and a reviewer publishes it, usually within a minute. Last touched 2026-10-09.

01edit any field on a page of its own
02a model checks it for accuracy and spam
03clean and confident goes live immediately

edit this record →back to the registry

Related Ports

all 66 in email →

the 8 most looked-up other ports in email — 66 ports carry that label.

port	service	proto	category	risk	views
:143	IMAP	TCPUDP	Email	caution	20.7k
:995	POP3S	TCPtls	Email	caution	18.8k
:109	POP2	TCP	Email	caution	17.9k
:2096	cPanel SSL Webmail	TCPtls	Web Services	safe	17.4k
:110	POP3	TCP	Email	caution	15.5k
:993	IMAPS	TCPtls	Email	caution	14.5k
:1352	Lotus Notes RPC	TCP	Email	caution	12.3k
:24	Private Mail	TCPUDP	Email	caution	11.7k

risk mix of the 8 listed

safe13%
caution88%

3 of 8 encrypted

Port :5766OpenMail NewMail Server

Technical Details

Security Information

Related Ports

Port 5766OpenMail NewMail Server