Port 642ESRO-EMSDP

Port assigned to ESRO-EMSDP V1.3, an Electronic Mail Submission and Delivery protocol.

transport: tcp · udp
in transit: cleartext
assignment: official
risk: 4/10
lookups: 0

Technical Details

what runs on :642

EMSD uses the Efficient Short Remote Operations (ESRO) transport and is assigned on both TCP and UDP port 642. It carries compact, ASN.1-encoded email operations for submission and delivery, rather than SMTP commands and line-oriented messages; the protocol is transaction-oriented and intended to reduce bandwidth and connection overhead. Normal deployments use the EMSD/ESRO protocol stack, not a web or generic mail protocol, and commonly interoperate through an EMSD gateway to conventional mail infrastructure.

Security Information

exposure of :642

risk score

4/ 10caution

worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.

email averages 3.2 across 62 ports — this one sits 0.8 above.

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

EMSD does not provide modern encryption by default, so message content and credentials or authentication exchanges should not be assumed confidential on the network. This obsolete and rarely observed service should generally be restricted to trusted hosts or protected with an appropriate secure tunnel; an exposed instance may provide an attacker with an email submission or delivery endpoint to probe for authentication and relay weaknesses.

Record

iana registry entry

port: :642
service: ESRO-EMSDP
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 4/10caution
category: Email
usage: This port is used by EMSD, a compact email submission and delivery protocol designed for constrained or low-bandwidth environments. Engineers may encounter it on legacy mobile-mail systems or gateways rather than on ordinary SMTP mail servers.
lookups: 0rank 993
added: 2026-09-15
updated: 2026-09-22
references: IANA service name registry — port 642

Something wrong?

This record is maintained by the engineers who use port 642. 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 62 in email →

the 8 most looked-up other ports in email — 62 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 :642ESRO-EMSDP

Technical Details

Security Information

Related Ports

Port 642ESRO-EMSDP