Service Name and Transport Protocol Port Number Registry

Last Updated
2026-05-11
Expert(s)
TCP/UDP: Joe Touch; Eliot Lear, Kumiko Ono, Wes Eddy, Brian Trammell,
and Michael Scharf
SCTP: Michael Tuexen
DCCP: Eddie Kohler and Yoshifumi Nishida
Reference
[RFC6335]
Note
Service names and port numbers are used to distinguish between different
services that run over transport protocols such as TCP, UDP, DCCP, and
SCTP.

Service names are assigned on a first-come, first-served process, as
documented in [RFC6335].

Port numbers are assigned in various ways, based on three ranges: System
Ports (0-1023), User Ports (1024-49151), and the Dynamic and/or Private
Ports (49152-65535); the different uses of these ranges are described in
[RFC6335]. According to Section 8.1.2 of [RFC6335], System Ports are 
assigned by the "IETF Review" or "IESG Approval" procedures described in 
[RFC8126]. User Ports are assigned by IANA using the "IETF Review" process, 
the "IESG Approval" process, or the "Expert Review" process, as per 
[RFC6335]. Dynamic Ports are not assigned.

The registration procedures for service names and port numbers are
described in [RFC6335].

Assigned ports both System and User ports SHOULD NOT be used without
or prior to IANA registration.

************************************************************************
* PLEASE NOTE THE FOLLOWING:                                           *
*                                                                      *
* ASSIGNMENT OF A PORT NUMBER DOES NOT IN ANY WAY IMPLY AN             *
* ENDORSEMENT OF AN APPLICATION OR PRODUCT, AND THE FACT THAT NETWORK  *
* TRAFFIC IS FLOWING TO OR FROM A REGISTERED PORT DOES NOT MEAN THAT   *
* IT IS "GOOD" TRAFFIC, NOR THAT IT NECESSARILY CORRESPONDS TO THE     *
* ASSIGNED SERVICE. FIREWALL AND SYSTEM ADMINISTRATORS SHOULD          *
* CHOOSE HOW TO CONFIGURE THEIR SYSTEMS BASED ON THEIR KNOWLEDGE OF    *
* THE TRAFFIC IN QUESTION, NOT WHETHER THERE IS A PORT NUMBER          *
* REGISTERED OR NOT.                                                   *
************************************************************************

Request an Assignment
  [https://www.iana.org/protocols/apply]

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Service Name Port Number Transport Protocol Description Assignee Contact Registration Date Modification Date Reference Service Code Unauthorized Use Reported Assignment Notes
24 tcp any private mail system [Rick_Adams] [Rick_Adams]
24 udp any private mail system [Rick_Adams] [Rick_Adams]
smtp 25 tcp Simple Mail Transfer [IESG] [IETF_Chair] 2017-06-05 [RFC-ietf-emailcore-rfc5321bis-43]
smtp 25 udp Simple Mail Transfer [IESG] [IETF_Chair] 2017-06-05 [RFC-ietf-emailcore-rfc5321bis-43]
re-mail-ck 50 tcp Remote Mail Checking Protocol [Steve_Dorner] [Steve_Dorner]
re-mail-ck 50 udp Remote Mail Checking Protocol [Steve_Dorner] [Steve_Dorner]
xns-mail 58 tcp XNS Mail [Susie_Armstrong] [Susie_Armstrong]
xns-mail 58 udp XNS Mail [Susie_Armstrong] [Susie_Armstrong]
finger 79 tcp Finger [David_Zimmerman] [David_Zimmerman] Unauthorized use by some mail users (see [RFC4146] for details)
finger 79 udp Finger [David_Zimmerman] [David_Zimmerman] Unauthorized use by some mail users (see [RFC4146] for details)
csnet-ns 105 tcp Mailbox Name Nameserver [Marvin_Solomon] [Marvin_Solomon]
csnet-ns 105 udp Mailbox Name Nameserver [Marvin_Solomon] [Marvin_Solomon]
pcmail-srv 158 tcp PCMail Server [Mark_L_Lambert] [Mark_L_Lambert]
pcmail-srv 158 udp PCMail Server [Mark_L_Lambert] [Mark_L_Lambert]
mailq 174 tcp MAILQ [Rayan_Zachariassen] [Rayan_Zachariassen]
mailq 174 udp MAILQ [Rayan_Zachariassen] [Rayan_Zachariassen]
qmtp 209 tcp The Quick Mail Transfer Protocol [D_J_Bernstein] [D_J_Bernstein] 2018-04-05
qmtp 209 udp The Quick Mail Transfer Protocol [D_J_Bernstein] [D_J_Bernstein] 2018-04-05
imap3 220 tcp Interactive Mail Access Protocol v3 [James_Rice] [James_Rice]
imap3 220 udp Interactive Mail Access Protocol v3 [James_Rice] [James_Rice]
imsp 406 tcp Interactive Mail Support Protocol [John_Myers] [John_Myers]
imsp 406 udp Interactive Mail Support Protocol [John_Myers] [John_Myers]
mailbox-lm 505 tcp mailbox-lm [Beverly_Moody] [Beverly_Moody]
mailbox-lm 505 udp mailbox-lm [Beverly_Moody] [Beverly_Moody]
biff 512 udp used by mail system to notify users of new mail received; currently receives messages only from processes on the same machine
dvl-activemail 1396 tcp DVL Active Mail
dvl-activemail 1396 udp DVL Active Mail
audio-activmail 1397 tcp Audio Active Mail
audio-activmail 1397 udp Audio Active Mail
video-activmail 1398 tcp Video Active Mail [Avshalom_Houri] [Avshalom_Houri]
video-activmail 1398 udp Video Active Mail [Avshalom_Houri] [Avshalom_Houri]
mailbox 2004 tcp
lnvmailmon 2285 tcp LNVMAILMON [John_Payne] [John_Payne]
lnvmailmon 2285 udp LNVMAILMON [John_Payne] [John_Payne]
mns-mail 2593 tcp MNS Mail Notice Service [Rumiko_Kikuta] [Rumiko_Kikuta]
mns-mail 2593 udp MNS Mail Notice Service [Rumiko_Kikuta] [Rumiko_Kikuta]
lotusmtap 3007 tcp Lotus Mail Tracking Agent Protocol [Ken_Lin] [Ken_Lin]
lotusmtap 3007 udp Lotus Mail Tracking Agent Protocol [Ken_Lin] [Ken_Lin]
ironmail 3206 tcp IronMail POP Proxy [Mike_Hudack] [Mike_Hudack]
ironmail 3206 udp IronMail POP Proxy [Mike_Hudack] [Mike_Hudack]
ccmail 3264 tcp cc:mail/lotus [brockman] [brockman]
ccmail 3264 udp cc:mail/lotus [brockman] [brockman]
mcs-fastmail 3302 tcp MCS Fastmail [Patti_Jo_Newsom] [Patti_Jo_Newsom]
mcs-fastmail 3302 udp MCS Fastmail [Patti_Jo_Newsom] [Patti_Jo_Newsom]
mcs-mailsvr 3332 tcp MCS Mail Server [Patti_Jo_Newsom] [Patti_Jo_Newsom]
mcs-mailsvr 3332 udp MCS Mail Server [Patti_Jo_Newsom] [Patti_Jo_Newsom]
webmail-2 3511 tcp WebMail/2 [Dimitris_Michelinaki] [Dimitris_Michelinaki] 2002-05
webmail-2 3511 udp WebMail/2 [Dimitris_Michelinaki] [Dimitris_Michelinaki] 2002-05
gbs-smp 3762 tcp GBS SnapMail Protocol [Eric_Harris_Braun] [Eric_Harris_Braun] 2003-06
gbs-smp 3762 udp GBS SnapMail Protocol [Eric_Harris_Braun] [Eric_Harris_Braun] 2003-06
mupdate 3905 tcp Mailbox Update (MUPDATE) protocol [RFC3656]
mupdate 3905 udp Mailbox Update (MUPDATE) protocol [RFC3656]
mailprox 3936 tcp Mailprox [Christof_Drescher] [Christof_Drescher] 2003-11
mailprox 3936 udp Mailprox [Christof_Drescher] [Christof_Drescher] 2003-11
minger 4069 tcp Minger Email Address Validation Service [Arvel_Hathcock] [Arvel_Hathcock] 2007-03
minger 4069 udp Minger Email Address Validation Service [Arvel_Hathcock] [Arvel_Hathcock] 2007-03
ds-mail 4405 tcp ASIGRA Televaulting Message Level Restore service
ds-mail 4405 udp ASIGRA Televaulting Message Level Restore service
openmail 5729 tcp Openmail User Agent Layer [OpenMail_Encyclopedi][Don_Loughry] [OpenMail_Encyclopedi][Don_Loughry]
openmail 5729 udp Openmail User Agent Layer [OpenMail_Encyclopedi][Don_Loughry] [OpenMail_Encyclopedi][Don_Loughry]
openmailg 5755 tcp OpenMail Desk Gateway server [OpenMail_Encyclopedi][Don_Loughry] [OpenMail_Encyclopedi][Don_Loughry]
openmailg 5755 udp OpenMail Desk Gateway server [OpenMail_Encyclopedi][Don_Loughry] [OpenMail_Encyclopedi][Don_Loughry]
x500ms 5757 tcp OpenMail X.500 Directory Server [OpenMail_Encyclopedi][Don_Loughry] [OpenMail_Encyclopedi][Don_Loughry]
x500ms 5757 udp OpenMail X.500 Directory Server [OpenMail_Encyclopedi][Don_Loughry] [OpenMail_Encyclopedi][Don_Loughry]
openmailns 5766 tcp OpenMail NewMail Server [OpenMail_Encyclopedi][Don_Loughry] [OpenMail_Encyclopedi][Don_Loughry]
openmailns 5766 udp OpenMail NewMail Server [OpenMail_Encyclopedi][Don_Loughry] [OpenMail_Encyclopedi][Don_Loughry]
s-openmail 5767 tcp OpenMail Suer Agent Layer (Secure) [OpenMail_Encyclopedi][Don_Loughry] [OpenMail_Encyclopedi][Don_Loughry]
s-openmail 5767 udp OpenMail Suer Agent Layer (Secure) [OpenMail_Encyclopedi][Don_Loughry] [OpenMail_Encyclopedi][Don_Loughry]
openmailpxy 5768 tcp OpenMail CMTS Server [OpenMail_Encyclopedi][Don_Loughry] [OpenMail_Encyclopedi][Don_Loughry]
openmailpxy 5768 udp OpenMail CMTS Server [OpenMail_Encyclopedi][Don_Loughry] [OpenMail_Encyclopedi][Don_Loughry]
http-wmap 8990 tcp webmail HTTP service [Chris_Newman] [Chris_Newman] 2007-12-03
http-wmap 8990 udp webmail HTTP service [Chris_Newman] [Chris_Newman] 2007-12-03
https-wmap 8991 tcp webmail HTTPS service [Chris_Newman] [Chris_Newman] 2007-12-03
https-wmap 8991 udp webmail HTTPS service [Chris_Newman] [Chris_Newman] 2007-12-03
xmltec-xmlmail 9091 tcp xmltec-xmlmail [Mitch_Kaufman] [Mitch_Kaufman]
xmltec-xmlmail 9091 udp xmltec-xmlmail [Mitch_Kaufman] [Mitch_Kaufman]
wmereceiving 11997 sctp WorldMailExpress [Greg_Foutz] [Greg_Foutz] 2006-03
wmedistribution 11998 sctp WorldMailExpress [Greg_Foutz] [Greg_Foutz] 2006-03
wmereporting 11999 sctp WorldMailExpress [Greg_Foutz] [Greg_Foutz] 2006-03
dmf-mail Digest Message Format for Mail
ehf-mail Encoding Header Field for Mail
imap2 Interim Mail Access Protocol version 2
mail Format of Electronic Mail Messages
pcmail Pcmail Transport Protocol
jmap tcp JSON Meta Application Protocol [IESG] [IETF_Chair] 2016-01-22 2019-07-16 [RFC8620] This service name was previously assigned under the name "JSON Mail Access Protocol". This has been de-assigned and re-assigned with the approval of the previous assignee.
mconnect ClairMail Connect [Sachin_Desai] [Sachin_Desai] Defined TXT keys: None
ni-mail tcp NI MAIL [Steve_Kille] [Steve_Kille] 2017-05-18 Defined TXT keys: None
ni-mail udp NI MAIL [Steve_Kille] [Steve_Kille] 2017-05-18 Defined TXT keys: None
pgpkey-mailto PGP Key submission using SMTP [Jeroen_Massar_3] [Jeroen_Massar_3] Defined TXT keys: user=<user portion of the mail address>
pstmailsync tcp File synchronization protocol for Pst Mail Sync [Arrow_Bit_SL] [Javier_Nigro] 2012-04-26 Defined TXT keys: uuid=<unique instance identifier>
pstmailsync-ssl tcp Secured file synchronization protocol for Pst Mail Sync [Arrow_Bit_SL] [Javier_Nigro] 2012-04-26 Defined TXT keys: uuid=<unique instance identifier>

Contact Information

ID Name Organization Contact URI Last Updated
[Arrow_Bit_SL] Arrow Bit SL mailto:info&arrowbit.com 2012-04-26
[Arvel_Hathcock] Arvel Hathcock mailto:arvel&altn.com 2007-03
[Avshalom_Houri] Avshalom Houri mailto:Avshalom&ubique.com
[Beverly_Moody] Beverly Moody mailto:Beverly_Moody&stercomm.com
[Chris_Newman] Chris Newman mailto:chris.newman&oracle.com 2017-01-26
[Christof_Drescher] Christof Drescher mailto:drescher&mailprox.net 2003-11
[D_J_Bernstein] D. J. Bernstein mailto:ports&box.cr.yp.to 2018-04-05
[David_Zimmerman] David Zimmerman mailto:dpz&rutgers.edu
[Dimitris_Michelinaki] Dimitris Michelinakis mailto:dimitris&michelinakis.gr 2002-05
[Don_Loughry] Don Loughry mailto:DON_LOUGHRY&hp-cupertino-om4.om.hp.com
[Eric_Harris_Braun] Eric Harris-Braun mailto:eric&glassbead.com 2003-06
[Greg_Foutz] Greg Foutz mailto:gregf&adminovation.com 2006-03
[IESG] IESG mailto:iesg&ietf.org
[IETF_Chair] IETF Chair IETF mailto:chair&ietf.org
[James_Rice] James Rice mailto:RICE&sumex-aim.stanford.edu
[Javier_Nigro] Javier Nigro Arrow Bit SL mailto:support&arrowbit.com 2012-04-26
[Jeroen_Massar_3] Jeroen Massar mailto:jeroen&unfix.org
[John_Myers] John Myers mailto:jgm+&cmu.edu
[John_Payne] John Payne mailto:jpayne&lotus.com
[Ken_Lin] Ken Lin mailto:klin&us.ibm.com
[Mark_L_Lambert] Mark L. Lambert mailto:markl&ptt.lcs.mit.edu
[Marvin_Solomon] Marvin Solomon mailto:solomon&cs.wisc.edu
[Mike_Hudack] Mike Hudack mailto:mike&mhudack.com
[Mitch_Kaufman] Mitch Kaufman mailto:mk&weconnectyou.com
[OpenMail_Encyclopedi] OpenMail Encyclopedia mailto:opencyc&hpopd.pwd.hp.com
[Patti_Jo_Newsom] Patti Jo Newsom mailto:pjn&mcsdallas.com
[Rayan_Zachariassen] Rayan Zachariassen mailto:rayan&ai.toronto.edu
[Rick_Adams] Rick Adams mailto:rick&uunet.uu.net
[Rumiko_Kikuta] Rumiko Kikuta mailto:kiku&nd.net.fujitsu.co.jp
[Sachin_Desai] Sachin Desai mailto:sachin&clairmail.com
[Steve_Dorner] Steve Dorner mailto:s-dorner&uiuc.edu
[Steve_Kille] Steve Kille mailto:steve.kille&isode.com 2017-05-18
[Susie_Armstrong] Susie Armstrong mailto:Armstrong.wbst128@xerox
[brockman] mailto:brockman&ccmail.com