Overview of services running on Port 25 TCP.
~13.57 Million IP addresses observed from May to December 2012
To get raw lists of the data go to Download. For an explanation of what this data is and how it was obtained, see Paper.

Servicename	Product	Count	Percent
smtp		4327153	31.892
smtp	Exim smtpd	2398928	17.68
smtp	Postfix smtpd	2036218	15.007
no match	-/-	1350690	9.955
smtp	Microsoft ESMTP	946369	6.975
smtp	Sendmail	724412	5.339
smtp	Microsoft Exchange smtpd	521383	3.843
smtp	Symantec Enterprise Security manager smtpd	256961	1.894
smtp	MailEnable smptd	191578	1.412
smtp	IdeaSmtpServer smtpd	138207	1.019
smtp	Cisco PIX sanitized smtpd	99732	0.735
smtp	Alt-N MDaemon mail server	68735	0.507
smtp	PowerMTA smtpd	60693	0.447
smtp	Barracuda Networks Spam Firewall smtpd	54870	0.404
smtp	rblsmtpd wrapped smtpd	51256	0.378
smtp	IMail NT-ESMTP	40020	0.295
smtp	Lotus Domino smtpd	20418	0.15
smtp-proxy	ESET NOD32 anti-virus smtp proxy	19775	0.146
smtp	Kerio Connect smtpd	14448	0.106
smtp	XMail SMTP server	14392	0.106
smtp	IceWarp smtpd	13188	0.097
smtp	WinWebMail smtpd	13040	0.096
smtp-proxy	spamd smtpd	10401	0.077
http	CCProxy	9112	0.067
smtp	Lyris ListManager smtpd	8704	0.064
smtp	Microsoft Exchange 2010 smtpd	7897	0.058
smtp	MailMarshal	7209	0.053
smtp	mailfront smtpd	7098	0.052
smtp	Communigate Pro SMTP	6397	0.047
smtp	Allworx 6x VoIP phone smtpd	6248	0.046
smtp	Merak Mail Server smtpd	5764	0.042
nagios-nsca	Nagios NSCA	5727	0.042
smtp	Symantec Messaging Gateway smtpd	5446	0.04
smtp	Surgemail smtpd	4869	0.036
smtp	RaidenMAILD smtpd	4619	0.034
smtp	JAMES smtpd	3809	0.028
smtp	Kerio MailServer	3780	0.028
smtp	Winmail smtpd	3675	0.027
smtp	Axigen smtpd	3255	0.024
smtp	Tobit David.fx smtpd	3219	0.024
smtp	hMailServer	3010	0.022
smtp	Cisco IronPort C160 firewall smtpd	2955	0.022
smtp	hMailServer smtpd	2871	0.021
http	SonicWALL	2622	0.019
smtp	Citadel smtpd	2593	0.019
http	letv	2546	0.019
smtp	NetBox smtpd	2355	0.017
smtp	ArGoSoft Mail Server Pro	2333	0.017
smtp	Brother printer smtpd	2220	0.016
chat	AIM or ICQ server	2190	0.016
http		2172	0.016
smtp	Novell GroupWise	2057	0.015
smtp	Unrecognized SMTP service	2044	0.015
smtp	eSafe mail gateway	1919	0.014
smtp	XWall smtpd	1716	0.013
socks-proxy	CCProxy socks proxy	1600	0.012
smtp	Novell NetWare GroupWise Internet Agent smtpd	1593	0.012
smtp	MailEnable Enterprise smptd	1460	0.011
smtp	Rockliffe MailSite	1459	0.011
smtp-proxy	MailFoundry antispam smtp proxy	1366	0.01
smtp-proxy	GData AntiVirenKit MailGateway smtp proxy	1358	0.01
smtp	StrongMail smtpd	1354	0.01
smtp	IA Mailserver smtpd	1349	0.01
smtp	Code-Crafters Ability Mail Server smtpd	1339	0.01
smtp-proxy	Symantec Brightmail smtp proxy	1320	0.01
smtp-proxy	CCProxy smtp proxy	1312	0.01
smtp	Post.Office	1278	0.009
smtp	FirstClass SMTP server	1278	0.009
smtp	Quarkmail smtpd	1234	0.009
smtp-proxy	UserGate smtp proxy	1231	0.009
smtp	DeskNow smtpd	1054	0.008
smtp-proxy	Scalix smtp relay	1053	0.008
smtp	ALT-N SecurityGateway smtpd	1053	0.008
smtp	Eudora EIMS X smtpd	1048	0.008
smtp	Network Box smtpd	1008	0.007
smtp	NTMail smtpd	1002	0.007
smtp	MAILsweeper SMTP proxy	875	0.006
smtp	MDaemon smtpd	802	0.006
smtp	SCO smtpd	787	0.006
smtp-proxy	Symantec Mail Security smtp proxy	741	0.005
ssh	OpenSSH	707	0.005
ftp	Microsoft ftpd	673	0.005
smtp	Sendmail Switch smtpd	672	0.005
smtp	ArGoSoft Mail Server Freeware	666	0.005
smtp	DvISE PostMan smtpd	662	0.005
smtp	SINA smtpd	613	0.005
smtp	Mail2000 smtpd	603	0.004
smtp	ArGoSoft Freeware smtpd	592	0.004
smtp	Cisco IOS NetWorks smtp server	586	0.004
smtp	qpsmtpd	558	0.004
smtp	LAN-ACES MERCUR smtp server	557	0.004
http	lighttpd	551	0.004
smtp	SoftStack Free SMTP Server	545	0.004
smtp	Webwasher CSM Suite smtpd	543	0.004
smtp	IMail smtpd	531	0.004
http	AIM	513	0.004
smtp	Trend Micro InterScan smtpd	510	0.004
smtp-proxy	McAfee EWSVA smtp proxy	492	0.004
smtp-proxy	McAfee EWSA 3100 smtp proxy	469	0.003
smtp-proxy	Net at Work Mail Gateway smtp proxy	461	0.003
smtp-proxy	McAfee EWSA 3200 smtp proxy	452	0.003
smtp	Sun Java System Messaging Server smtpd	447	0.003
smtp	Canon printer smtp server	440	0.003
smtp	Mirapoint smtpd	423	0.003
smtp	Mirapoint Messaging Server MOS smtpd	396	0.003
http	Apache	389	0.003
http-proxy	CCProxy http proxy	383	0.003
ftp		381	0.003
smtp	WebEasyMail smtpd	346	0.003
smtp	VisNetic MailServer	339	0.002
smtp	MailMax smtpd	334	0.002
telnet		329	0.002
smtp-proxy	Python SMTP Proxy	324	0.002
smtp	Eudora smtpd	324	0.002
smtp	Microsoft SMTP	309	0.002
smtp	Konica Minolta bizhub 350 printer smtpd	301	0.002
http	Microsoft IIS httpd	299	0.002
smtp	AnNyung smtpd	296	0.002
smtp	Oki 3200N laser printer smtpd	288	0.002
smtp	Youngzsoft CMailServer smtpd	285	0.002
smtp-proxy	McAfee EWSA 3300 smtp proxy	275	0.002
smtp	Mitel 3300 PBX smtpd	270	0.002
smtp	mxl smtpd	260	0.002
smtp	OpenVMS smtpd	256	0.002
smtp	Messaging Architects M+ Extreme Email Engine smtpd	253	0.002
smtp-proxy	AnalogX SMTP proxy	247	0.002
ftp	Serv-U ftpd	241	0.002
smtp	Panasonic smtpd	228	0.002
smtp	Dumbster fake smtpd	210	0.002
smtp	InterMail smtpd	208	0.002
smtp-proxy	McAfee EGVA smtp proxy	204	0.002
smtp	LSMTP smtpd	200	0.001
smtp	Bizanga bizsmtp smtpd	196	0.001
http	Microsoft HTTPAPI httpd	181	0.001
smtp-proxy	McAfee EWSA 3000 smtp proxy	176	0.001
smtp-proxy	PGP Universal smtp proxy	174	0.001
smtp	Floosietek FTGate smtpd	166	0.001
telnet	Linux telnetd	161	0.001
smtp	JAMES 3 M3 smtpd	159	0.001
smtp	PSCS VPOP3 mail server	158	0.001
smtp	Trend Micro InterScan	154	0.001
telnet	Netgear broadband router or ZyXel VoIP adapter telnetd	151	0.001
smtp	Mailtraq smtpd	147	0.001
smtp-proxy	Trend Micro IMSS smtp proxy	146	0.001
ssh	Dropbear sshd	141	0.001
smtp	Novonyx Novell NetMail smtpd	138	0.001
smtp-proxy	EdgeWave MAG3000 Email Filtering appliance smtp proxy	136	0.001
http	GoAhead-Webs httpd	135	0.001
ftp	FileZilla ftpd	133	0.001
smtp	WinRoute Pro smtpd	132	0.001
smtp	OpenSMTPD	130	0.001
smtp	ArGoSoft Mail Server Plus	130	0.001
smtp	WorkgroupMail smtpd	129	0.001
smtp	PMDF smtpd	123	0.001
ftp	ProFTPD	117	0.001
smtp-proxy	SpamFilterISP smtp proxy	116	0.001
smtp-proxy	McAfee ESA3400 smtp proxy	110	0.001
http-proxy	Squid http proxy	105	0.001
ssh		101	0.001
smtp	SLmail smtpd	101	0.001
smtp	Sun iPlanet smtpd	100	0.001
smtp	qmail smtpd	99	0.001
smtp	Trend Micro InterScan VirusWall SMTP	98	0.001
smtp	MessageWall SMTP proxy	96	0.001
ftp	vsftpd	96	0.001
ftp	MikroTik router ftpd	93	0.001
openvpn	OpenVPN	91	0.001
http	Apache Tomcat/Coyote JSP engine	89	0.001
smtp	ModusMail smtpd	86	0.001
smtp	Stalker smtpd	83	0.001
smtp-proxy	McAfee SCM3100 smtp proxy	83	0.001
smtp-proxy	McAfee EG5000 smtp proxy	83	0.001
501		83	0.001
smtp	4D WebSTAR smtpd	82	0.001
smtp-proxy	Symantec SGS smtp proxy	78	0.001
smtp	Norton Antivirus Gateway NAVGW	78	0.001
smtp	Mercury/32 smtpd	78	0.001
smtp	OpenBSD spamd	74	0.001
http	Boa HTTPd	72	0.001
smtp	Oracle Communications Message Exchange imapd	70	0.001
ssh	MikroTik RouterOS sshd	69	0.001
http	thttpd	69	0.001
telnet	Draytek Vigor ADSL router telnetd	68	0.001
smtp	Netscape Messaging Server	66	0.0
smtp-proxy	Proxy+ smtp proxy	65	0.0
smtp	Mercury smtpd	65	0.0
smtp	Smail-ESMTP	63	0.0
smtp-proxy	McAfee EG4500 smtp proxy	63	0.0
smtp	IBM AS/400 smtpd	59	0.0
smtp	CommuniGate Pro mail server	59	0.0
502		59	0.0
smtp	WebSTAR SMTP server	57	0.0
smtp	Neon Mail Server smtpd	56	0.0
smtp-proxy	Altospam smtp proxy	55	0.0
smtp	SmarterMail smtpd	54	0.0
smtp	Process Software smtpd	53	0.0
smtp	Nemesis smtpd	52	0.0
221		51	0.0
smtp-proxy	602LAN Suite smtpd	50	0.0
smtp	eXtremail smtpd	50	0.0
vnc	VNC	48	0.0
smtp	ZMailer smtpd	48	0.0
smtp	DynFX smtpd	48	0.0
smtp	TurboSendmail smtpd	46	0.0
smtp-proxy	McAfee EG4000 smtp proxy	46	0.0
smtp	Postini smtpd	46	0.0
ftp	Pure-FTPd	46	0.0
smtp-proxy	McAfee EG5500 smtp proxy	44	0.0
smtp-proxy	F-Secure AV SMTP Proxy	44	0.0
smtp-proxy	F-Secure Internet Gateway SMTP proxy	43	0.0
smtp	IA eMailServer Corporate	43	0.0
http	nginx	43	0.0
smtp	SMTPBeamer smtpd	42	0.0
http	Netwave IP camera http config	42	0.0
ssh	WeOnlyDo sshd	39	0.0
mongodb	MongoDB	39	0.0
smtp	Synchronet smtpd	37	0.0
ssl	SSLv3	35	0.0
smtp	AppleMailServer	32	0.0
ftp	Dreambox ftpd	32	0.0
smtp-proxy	BitDefender anti-virus mail gateway	31	0.0
smtp	MailEnable Enterprise	31	0.0
smtp	Worldmail smtpd	30	0.0
smtp-proxy	1st SMTP relay	30	0.0
mysql	MySQL	30	0.0
smtp	True North Internet Anywhere smtpd	29	0.0
smtp	Classic Hamster smtpd	29	0.0
smtp	AVM KEN! smtpd	27	0.0
smtp	Windows NT SMTP Server smtpd	26	0.0
http	Hikvision-Webs	26	0.0
http	Avtech AVN801 network camera	24	0.0
ftp	Netgear broadband router or ZyXel VoIP adapter ftpd	24	0.0
ssh	Bitvise WinSSHD	23	0.0
smtp-proxy	SnertSoft Barricade MX smtp proxy	23	0.0
smtp	odmrd	22	0.0
http	PDR-M800	22	0.0
smtp-proxy	McAfee EWSA 3400 smtp proxy	21	0.0
smtp-proxy	McAfee ESA3300 smtp proxy	21	0.0
xml		20	0.0
telnet	Allied Telesis x900-series switch telnetd	20	0.0
smtp	Smap	20	0.0
smtp-proxy	Smart-Soft spam filtering smtp-proxy	20	0.0
smtp-proxy	McAfee SCM3200 smtp proxy	20	0.0
smtp-proxy	McAfee S120 smtp proxy	20	0.0
smtp-proxy	McAfee SCM3000 smtp proxy	19	0.0
directconnect	Direct Connect P2P	19	0.0
telnet	Moxa NPort 5130 serial-to-IP converter telnetd	18	0.0
smtp	L-Soft HDMail smtpd	18	0.0
smtp	IBM MVS smtpd	18	0.0
smtp	DavMail smtpd	18	0.0
pop3	Microsoft Windows 2003 POP3 Service	18	0.0
ftp	DrayTek Vigor 2820 ADSL router ftpd	18	0.0
500		18	0.0
smtp	Maillennium smtpd	17	0.0
smtp	VisNetic MailScan ESMTP server	16	0.0
smtp	Nortel CallPilot imapd	16	0.0
smtp	GMX smtpd	16	0.0
http	DD-WRT milli_httpd	16	0.0
telnet	Cisco 1721 router telnetd	15	0.0
smtp	fssmtpd	15	0.0
http	Mbedthis-Appweb	15	0.0
http	Cross Web Server	15	0.0
ssl	TLS	14	0.0
smtp-proxy	McAfee EG3200 smtp proxy	14	0.0
smtp-proxy	McAfee EG3100 smtp proxy	14	0.0
http	mini_httpd	14	0.0
smtp-proxy	McAfee ESVA smtp proxy	13	0.0
smtp	IBM VM smtpd	13	0.0
ftp	Gene6 ftpd	13	0.0
smtp	MailGate smtpd	12	0.0
smtp	HP Service Desk SMTP server	12	0.0
vnc	RealVNC Enterprise	11	0.0
smtp	IA eMailServer Standard	11	0.0
smtp	ArGoSoft Pro smtpd	11	0.0
http	Jetty	11	0.0
http	http server 1.0	11	0.0
ftp	Synology DiskStation NAS ftpd	11	0.0
smtp-proxy	Tumbleweed smtp proxy	10	0.0
smtp-proxy	McAfee SCM3300 smtp proxy	10	0.0
smtp-proxy	Alligate smtp proxy	10	0.0
smtp	LiteMail smtpd	10	0.0
smtp	Hornbill Supportworks smtpd	10	0.0
smtp	Epiphany Campaign Manager for Email (CME) smtpd	10	0.0
smtp	Coremail smtpd	10	0.0
smtp	Communigate Pro smtpd	10	0.0
http-proxy	F5 BIG-IP load balancer http proxy	10	0.0