Port 406Interactive Mail Support Protocol

Port 406 is assigned to the Interactive Mail Support Protocol for interactive mail services.

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

also known as imsp

Technical Details

what runs on :406

no technical write-up for :406 yet

the handshake, the implementations you meet in the wild, the flags that matter. we have the registry entry — the detail comes from the engineers who run it.

add technical details

Security Information

exposure of :406

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 3.6 across 47 ports — this one sits 2.6 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 :406 yet

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

Record

iana registry entry

port: :406
service: Interactive Mail Support Protocol
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 1/10safe
category: Email
usage: IANA assigns TCP and UDP port 406 to the Interactive Mail Support Protocol. The assignment is registered to John Myers, but there is insufficient public deployment information to identify a current implementation or typical operator.
lookups: 0rank 994
added: 2026-08-26
updated: 2026-08-26
references: IANA service name registry — port 406

Something wrong?

This record is maintained by the engineers who use port 406. 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 2026-08-26.

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 47 in email →

the 8 most looked-up other ports in email — 47 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 :406Interactive Mail Support Protocol

Technical Details

Security Information

Related Ports

Port 406Interactive Mail Support Protocol