Overview of services running on Port 26 TCP.
~721 Thousand 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	Version	Count	Percent
smtp	Exim smtpd	4.77	457596	63.451
smtp	Exim smtpd	4.76	92688	12.852
smtp	Exim smtpd	4.69	42744	5.927
smtp			27249	3.778
no match	-/-	-/-	21795	3.022
smtp	Postfix smtpd		10387	1.44
http			9263	1.284
smtp	Microsoft ESMTP	6.0.3790.4675	6305	0.874
smtp	Exim smtpd		5136	0.712
smtp	Sendmail		3755	0.521
http	SonicWALL		3627	0.503
smtp	Microsoft Exchange smtpd		2453	0.34
chat	AIM or ICQ server		2187	0.303
smtp	Exim smtpd	4.63	1507	0.209
smtp	Microsoft ESMTP	6.0.3790.3959	1119	0.155
http-proxy	Squid http proxy	2.6.STABLE13	1062	0.147
smtp	Sendmail	8.14.3/8.14.3	1060	0.147
arcserve	ARCserve Discovery		993	0.138
ssh	OpenSSH	4.3	987	0.137
smtp	MailEnable smptd	1.986--	980	0.136
smtp	Symantec Enterprise Security manager smtpd		961	0.133
ssl	SSLv3		918	0.127
smtp	Microsoft ESMTP	5.0.2195.6713	878	0.122
http	Apache	2.2.8	723	0.1
telnet	QDX 6000 Console Utility		714	0.099
smtp	Sendmail	8.13.8/8.13.8	684	0.095
http	AIM	1.0	618	0.086
ftp	Microsoft ftpd		485	0.067
ssh	Dropbear sshd	0.49	478	0.066
smtp	Microsoft ESMTP	5.0.2195.7381	471	0.065
smtp	Sendmail	8.14.4/8.14.4	459	0.064
smtp	Sendmail	8.13.1/8.13.1	443	0.061
http	lighttpd	1.4.19	443	0.061
ssh	MikroTik RouterOS sshd		425	0.059
http	lighttpd	1.4.29	424	0.059
smtp	MailEnable smptd	0-3.63-	391	0.054
smtp	MailEnable smptd	0-3.62-	324	0.045
ssh	OpenSSH	4.2p1	311	0.043
smtp	MailEnable smptd	4.26--	306	0.042
telnet			292	0.04
smtp	Exim smtpd	4.70	271	0.038
smtp	MailEnable smptd	0-2.53-	263	0.036
telnet	Intel telnetd		262	0.036
smtp	MailEnable smptd	1.983--	256	0.035
smtp	Exim smtpd	4.64	254	0.035
http	a_63		240	0.033
telnet	K80 Console Utility		231	0.032
smtp	MailEnable smptd	5.10--	218	0.03
smtp	MailEnable smptd	0-5.51-	207	0.029
smtp	Axigen smtpd		192	0.027
smtp	rblsmtpd wrapped smtpd		186	0.026
smtp	Microsoft ESMTP	6.0.3790.1830	185	0.026
ssh	OpenSSH	5.5p1 Debian 6	183	0.025
ssh	OpenSSH	4.2	183	0.025
ssh	OpenSSH	2.3.0 mikrotik 2.9	176	0.024
smtp	Exim smtpd	4.67	169	0.023
smtp	MailEnable smptd	-3.61-	159	0.022
smtp	Exim smtpd	4.72	158	0.022
smtp	MailEnable smptd	5.11--	157	0.022
ssh	OpenSSH	5.1p1 Debian 5	156	0.022
ssh			151	0.021
http	Microsoft IIS httpd	6.0	150	0.021
ftp			146	0.02
smtp	Exim smtpd	4.71	136	0.019
telnet	Draytek Vigor ADSL router telnetd		133	0.018
http-proxy	Squid http proxy	3.0.PRE6+PatchSets-20070623	132	0.018
ssh	OpenSSH	5.8p1-hpn13v10	131	0.018
smtp	MailEnable smptd	1.981--	126	0.017
smtp	Exim smtpd	4.68	125	0.017
ssh	OpenSSH	5.3	118	0.016
smtp	Microsoft Exchange 2010 smtpd		109	0.015
http	Microsoft HTTPAPI httpd	2.0	107	0.015
http	GoAhead-Webs httpd		105	0.015
ssh	OpenSSH	5.4p1	104	0.014
http	Netwave IP camera http config		104	0.014
smtp	Sendmail	8.14.3/8.14.3/Debian-5+lenny1	102	0.014
smtp	Barracuda Networks Spam Firewall smtpd		102	0.014
smtp	Exim smtpd	4.50	98	0.014
ssh	OpenSSH	5.3p1 Debian 3ubuntu7	95	0.013
ssh	OpenSSH	5.2	95	0.013
smtp	Microsoft ESMTP	7.5.7601.17514	93	0.013
smtp	Exim smtpd	4.75	93	0.013
ssh	Dropbear sshd	0.52	91	0.013
ssh	OpenSSH	4.5p1	90	0.012
telnet	Linux telnetd		88	0.012
ssh	OpenSSH	5.5p1 Debian 6+squeeze2	84	0.012
smtp	IMail NT-ESMTP	11.03 1-1	84	0.012
smtp	Alt-N MDaemon mail server	11.0.3	82	0.011
smtp	MailEnable smptd	0-3.6-	81	0.011
http	Apache Tomcat/Coyote JSP engine	1.1	81	0.011
smtp	MailEnable smptd	3.62--	80	0.011
smtp	Exim smtpd	3.36	80	0.011
smtp	MailEnable smptd	5.51--5.51	79	0.011
smtp	MailEnable smptd	4.23--	77	0.011
ssh	OpenSSH	5.1p1	76	0.011
http	Microsoft IIS httpd		74	0.01
smtp	MailEnable smptd	0-3.14-	73	0.01
smtp	IMail NT-ESMTP	11.03 2-1	73	0.01
smtp	Rockliffe MailSite	9.5.4.3	71	0.01
smtp	MailEnable smptd	0-6.02-	70	0.01
ssh	OpenSSH	5.1	69	0.01
smtp	Allworx 6x VoIP phone smtpd		69	0.01
ftp	Serv-U ftpd	6.4	68	0.009
http	Apache		67	0.009
ssh	SCS sshd	3.2.9.1	64	0.009
smtp	Microsoft ESMTP	7.0.6002.18264	64	0.009
ssh	OpenSSH	5.5p1 Debian 6+squeeze1	63	0.009
http	Avtech AVN801 network camera	1.0	63	0.009
ftp	vsftpd	2.0.8 or later	63	0.009
ssh	OpenSSH	5.4	62	0.009
ssh	OpenSSH	4.4	62	0.009
ssh	OpenSSH	5.8	61	0.008
smtp	MailEnable smptd	6.0--	61	0.008
ssh	OpenSSH	5.6	55	0.008
smtp	MailEnable smptd	6.01--	55	0.008
smtp	Sendmail	8.14.2/8.14.2	54	0.007
ssh	OpenSSH	3.9p1	52	0.007
http-proxy	Squid http proxy	2.6.STABLE12	52	0.007
http	Hikvision-Webs		52	0.007
ssh	Dropbear sshd	0.51	51	0.007
smtp	Sendmail	8.14.3/8.14.3/Debian-9.4	51	0.007
smtp	Exim smtpd	4.73	51	0.007
vnc	VNC		49	0.007
pop3	hMailServer pop3d		49	0.007
smtp	MailEnable smptd	6.5--6.5	48	0.007
smtp	MailEnable smptd	6.53--	48	0.007
smtp	MailEnable smptd	6.03--	47	0.007
smtp	MailEnable smptd	1.9--	45	0.006
ssh	OpenSSH	5.9p1 Debian 5ubuntu1	44	0.006
ssh	OpenSSH	5.5	43	0.006
smtp	Cisco PIX sanitized smtpd		42	0.006
http	PDR-M800	1.0	42	0.006
smtp	Sendmail	8.12.11.20060308/8.12.11	41	0.006
smtp	Merak Mail Server smtpd	8.0.3	41	0.006
smtp	MailEnable smptd	4.22--	41	0.006
smtp	IceWarp smtpd	9.3.2	41	0.006
smtp	Sendmail	8.12.8/8.12.8	40	0.006
ftp	Serv-U ftpd	6.3	40	0.006
ssh	OpenSSH	3.6.1p2	39	0.005
smtp	MailEnable smptd	5.51--	39	0.005
smtp	MailEnable smptd	0-3.61-	38	0.005
ssh	Dropbear sshd	0.53.1	37	0.005
smtp	MailEnable smptd	5.03--	37	0.005
smtp	MailEnable smptd	--3.63	37	0.005
smtp	MailEnable smptd	0-6.53-	37	0.005
smtp	MailEnable Enterprise smptd	3.10	37	0.005
smtp	MDaemon smtpd	9.5.2	36	0.005
http	CCProxy		36	0.005
smtp	Sendmail	8.14.3/8.13.4	35	0.005
smtp	Alt-N MDaemon mail server	12.5.6	35	0.005
ssh	OpenSSH	5.8p1 Debian 7ubuntu1	34	0.005
smtp	RaidenMAILD smtpd	1916	34	0.005
smtp-proxy	ESET NOD32 anti-virus smtp proxy		34	0.005
smtp	MailEnable smptd	0-2.37-	34	0.005
smtp	Kerio Connect smtpd	7.4.0	34	0.005
smtp	Alt-N MDaemon mail server	10.0.0	34	0.005
http	Apache	2.2.14	34	0.005
smtp	Microsoft ESMTP	7.0.6002.18222	33	0.005
smtp	Surgemail smtpd	6.0a5-5	32	0.004
smtp	MailEnable smptd	0-5.10-	32	0.004
napster	WinMX or Lopster Napster P2P client		32	0.004
http	Boa HTTPd	0.94.13	32	0.004
ftp	Pure-FTPd		32	0.004
smtp	MailEnable smptd	6.5--	31	0.004
smtp	Sendmail	8.14.3/8.14.2	29	0.004
smtp	MDaemon smtpd	12.5.3	29	0.004
http	mini_httpd	1.19 19dec2003	29	0.004
ftp	Dreambox ftpd		29	0.004
ssh	OpenSSH	5.8p1 Debian 1ubuntu3	28	0.004
ssh	OpenSSH	5.4p1_hpn13v11	28	0.004
ssh	OpenSSH	4.3p2 Debian 9etch3	28	0.004
smtp-proxy	UserGate smtp proxy		28	0.004
smtp	MailEnable smptd	0-4.22-	28	0.004
smtp	MailEnable smptd	0-1.87-	28	0.004
ssl	Microsoft IIS SSL		27	0.004
ssh	OpenSSH	4.6	27	0.004
smtp	Sendmail	8.13.8/8.13.1	27	0.004
smtp	MailEnable smptd	-4.26-	27	0.004
smtp	MailEnable smptd	4.17--	27	0.004
http-proxy	Squid http proxy	2.7.STABLE9	26	0.004
ftp	Microsoft ftpd	5.0	26	0.004
ssh	OpenSSH	3.8.1p1	25	0.003
smtp	Sendmail	8.14.5/8.14.5	25	0.003
smtp	MailEnable smptd	0-4.26-	25	0.003
smtp	Alt-N MDaemon mail server	11.0.0	25	0.003
smtp	Microsoft ESMTP	7.5.7600.16601	24	0.003
smtp	Alt-N MDaemon mail server	12.5.4	24	0.003
http	Apache	2.2.3	24	0.003
http	Apache	2.2.22	24	0.003
ftp	Synology DiskStation NAS ftpd		24	0.003
smtp	MailEnable smptd	0-6.52-	23	0.003
smtp	Exim smtpd	4.62	23	0.003
smtp	Communigate Pro SMTP	4.3.9	23	0.003
smtp	Alt-N MDaemon mail server	10.1.0	23	0.003
http	thttpd		23	0.003
http	GoAhead-Webs		23	0.003
http	Boa HTTPd	0.94.14rc21	23	0.003
ftp	ProFTPD		23	0.003
ssh	OpenSSH	5.8p2_hpn13v11	22	0.003
ssh	OpenSSH	4.5	22	0.003
smtp	Symantec Messaging Gateway smtpd		22	0.003
smtp	Sendmail	8.13.4/8.13.4/Debian-3sarge3	22	0.003
smtp	Rockliffe MailSite	9.5.4.5	22	0.003
smtp	RaidenMAILD smtpd	2103	22	0.003
smtp	MailEnable smptd	4.25--	22	0.003
smtp	MailEnable smptd	-2.40-	22	0.003
smtp	MailEnable smptd	0-2.36-	22	0.003
smtp	Kerio Connect smtpd	7.3.2	22	0.003
smtp	Cisco IronPort C160 firewall smtpd		22	0.003
smtp	MailEnable smptd	4.25--4.26	21	0.003
smtp	MailEnable smptd	-2.53-	21	0.003
smtp	MailEnable smptd	0-5.53-	21	0.003
smtp	MailEnable Enterprise smptd	2.53	21	0.003
ftp	ProFTPD	1.3.1	21	0.003
ftp	FileZilla ftpd	0.9.40 beta	21	0.003
telnet	Cisco 1721 router telnetd		20	0.003
ssh	OpenSSH	3.5p1	20	0.003
ssh	Dropbear sshd	0.50	20	0.003
smtp	XMail SMTP server	1.27	20	0.003
smtp	MailEnable smptd	0-6.03-	20	0.003
smtp	MailEnable smptd	0-4.11-	20	0.003
http	Mbedthis-Appweb	2.0.4	20	0.003
http	Apache	2.2.16	20	0.003
ftp	FileZilla ftpd	0.9.41 beta	20	0.003
smtp	Sendmail	8.14.5/8.14.4	19	0.003
smtp	Kerio Connect smtpd	7.4.1	19	0.003
http	Apache	2.0.53	19	0.003
ssh	OpenSSH	5.2p1	18	0.002
smtp	RaidenMAILD smtpd	2001	18	0.002
smtp	Microsoft ESMTP	6.0.3790.211	18	0.002
telnet	Netopia ADSL router telnetd		17	0.002
ssh	OpenSSH	5.9p1-hpn13v11	17	0.002
ssh	OpenSSH	5.9	17	0.002
ssh	OpenSSH	4.7	17	0.002
smtp	MailEnable smptd	0-1.82-	17	0.002
smtp	Kerio Connect smtpd	7.3.1 patch 2	17	0.002
smtp	IMail NT-ESMTP	11.03 3-1	17	0.002
smtp	Exim smtpd	4.74	17	0.002
ftp	FileZilla ftpd	0.9.37 beta	17	0.002
ssh	OpenSSH	4.7p1 Debian 8ubuntu3	16	0.002
smtp	MailEnable Enterprise smptd	2.40	16	0.002
smtp	Kerio MailServer	6.7.0	16	0.002
smtp	ArGoSoft Mail Server Pro	1.8.9.6	16	0.002
http	Cross Web Server		16	0.002
ssh	OpenSSH	6.0	15	0.002
ssh	OpenSSH	4.7p1 Debian 8ubuntu1.2	15	0.002
smtp	RaidenMAILD smtpd	1917	15	0.002
smtp	MailEnable smptd	0-4.01-	15	0.002
smtp	IceWarp smtpd	9.1.0	15	0.002
smtp	Communigate Pro SMTP	5.4.1	15	0.002
http	thttpd	2.25b	15	0.002
http	Gadspot/Avtech AV787 webcam http config		15	0.002
http	Apache	2.2.9	15	0.002
http	Apache	2.2.17	15	0.002