Port 2390RSMTP

RSMTP is an obscure mail-related service assigned to Geoff Collyer on TCP and UDP port 2390.

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

Technical Details

what runs on :2390

RSMTP is registered on port :2390 over tcp and udp to Geoff Collyer. 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 :2390

this machine

# linux
sudo ss -tulpn 'sport = :2390'

# macos / bsd
sudo lsof -nP -i :2390

# windows (then: tasklist /FI "PID eq <pid>")
netstat -ano | findstr :2390

another host

nmap -sV -p T:2390 <host>
sudo nmap -sU -sV -p U:2390 <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 :2390

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 3.3 across 58 ports — this one sits 2.3 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 :2390 yet

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

Record

iana registry entry

port: :2390
service: RSMTP
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 1/10safe
category: Email
usage: Port 2390 is assigned to RSMTP over both TCP and UDP. The assignment is registered to Geoff Collyer, but there is no indication of widespread deployment or a documented implementation.
lookups: 0rank 993
added: 2026-09-22
updated: 2026-09-22
references: IANA service name registry — port 2390

Something wrong?

This record is maintained by the engineers who use port 2390. 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 2026-09-22.

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 58 in email →

the 8 most looked-up other ports in email — 58 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 :2390RSMTP

Technical Details

Security Information

Related Ports

Port 2390RSMTP