Uwe Ohse

SMTP server survey 19971031

Using a list of 5200 domain- and hostnames and IP Adresses as input i started a script which connected:

to each machine having an A DNS entry (or a cname pointing to one).
each of the MX hosts.

Duplicates were eliminated:

each IP address was connected only once to.
the script closed the connection if it had seen the connection reply before.
the script closed the connection if it had seen the ehlo or helo reply before.

This catched most but not all of the duplicates. It recognizes duplicate sendmails one virtual web servers (for example), but some other software uses different host names for each of the machines virtual addresses (especially the Internet Shopper).
The hostname list was collected from

sender and recipient addresses of messages passing through the NRW.NET mail servers.
relay hosts of that messages (either the machine handing the mail to our server or the machine we sent the mail to).
the list of hosts for which we relay.

I planned to do a survey of mail servers in active use, not the poor unmaintained, forgotton machines in dark rooms which nobody uses the mail. I hope i've accomplished that goal (it seems so - two thirds of the sendmails are running version 8.8 and higher).

The list of 5200 host/domain named lead to:

774 failed connections:
- 284 Connection refused
- 283 Connection establishment timeouts (i used 30 seconds as timeout).
- 143 No route to host
- 35 Timeouts occured during the connection.
- 33 Network is unreachble timeout. i'll do better next time). This number includes connection establishment timeouts and timeouts during the connection.
- 1 Protocol not available
401 recognized duplicate connections.
2988 successfull connections.

The script does send:

EHLO csl18.csl-gmbh.net
HELO csl18.csl-gmbh.net if the EHLO was not successful.
HELP the reponse was mainly used to recognize some mailers.
MAIL FROM: with varying some.domain.
RCPT TO:
QUIT

Another script check the replys and did some statistics.

EHLO-Test:

who many machines accepted the EHLO command? (which RFC 1425 defined in February 1993)
2654 knew EHLO (88.85)
333 did not know EHLO (11.14)

HELP-Test:

who many machines accepted the HELP command?
2676 sent HELP (89.58)
311 did not HELP (10.41)

Relaytest:

how many machines seem to let anybody relay spam?
2142 are possibly open (72.58)
809 didn't relay (27.41)
(ashaming numbers)

Software list:

interesting numbers. And many programs i didn't know before

   2022 Sendmail (67.67)
    103 Smail ( 3.44)
     94 Post.Office ( 3.14)
     93 Netscape Mail server ( 3.11)
     91 NT Mail ( 3.04)
     74 qmail ( 2.47)
     52 PP ( 1.74)
     45 Mercury ( 1.50)
     44 MS Exchange ( 1.47)
     40 unknown ( 1.33)
     34 Exim ( 1.13)
     31 Lotus SMTP MTA ( 1.03)
     29 ZMailer ( 0.97)
     29 PMDF ( 0.97)
     18 Eudora Internet Mail Server ( 0.60)
     18 Apple Internet Mail Server ( 0.60)
     15 MS SMTP Mail ( 0.50)
     13 MMDF ( 0.43)
     11 IMail ( 0.36)
     10 Mail.Hub TurboSendmail ( 0.33)
      9 Mercur ( 0.30)
      9 IBM VM SMTP ( 0.30)
      8 SLMail ( 0.26)
      8 InterScan VirusWall ( 0.26)
      7 AltaVista Firewall ( 0.23)
      7 LSMTP ( 0.23)
      7 Wrapper, maybe for Smail ( 0.23)
      6 InterLock ( 0.20)
      5 Raptor Firewall ( 0.16)
      5 UCX ( 0.16)
      5 MDaemon ( 0.16)
      5 TFS Gateway ( 0.16)
      4 GroupWise ( 0.13)
      4 MailSite SMTP Receiver ( 0.13)
      3 LetterRip ( 0.10)
      3 PowerWeb ( 0.10)
      2 Integralis SMTP Receiver ( 0.06)
      2 Connect2-SMTP ( 0.06)
      2 TGV/MultiNet, now cisco ( 0.06)
      2 Soft-Switch LMS ( 0.06)
      2 Major BBS ( 0.06)
      2 FirstClass Mail Server ( 0.06)
      1 MX ( 0.03)
      1 EMWACS IMS ( 0.03)
      1 David PostMan ( 0.03)
      1 iSMTP ( 0.03)
      1 NASTA Gate SMTP Server ( 0.03)
      1 FirstClass BBS ( 0.03)
      1 MS Mail SMTP Gateway ( 0.03)
      1 Mail.Link ( 0.03)
      1 Cyberguard or so ( 0.03)
      1 ISOCOR ( 0.03)
      1 Hawkeye SMTP ( 0.03)
      1 Worldgroup ( 0.03)
      1 Advox Omnigate ( 0.03)
      1 GroupMaster ( 0.03)
      1 Hummingbird SMTPD ( 0.03)

Software versions:

  Advox Omnigate:
        1 Advox Omnigate/4.02b
  AltaVista Firewall:
        3 AltaVista Firewall/1.27.1.1
        1 AltaVista Firewall/1.41
        1 AltaVista Firewall/1.42
        1 AltaVista Firewall/1.0
        1 AltaVista Firewall/1.27
  Apple Internet Mail Server:
       11 Apple Internet Mail Server/1.1.1
        5 Apple Internet Mail Server/1.0
        2 Apple Internet Mail Server/1.1
  Connect2-SMTP:
        1 Connect2-SMTP/4.30A
        1 Connect2-SMTP/4.00
  Cyberguard or so:
        1 Cyberguard or so/3.0
  David PostMan:
        1 David PostMan/unknown
  EMWACS IMS:
        1 EMWACS IMS/0.83
  Eudora Internet Mail Server:
       10 Eudora Internet Mail Server/1.2
        6 Eudora Internet Mail Server/1.1.2
        1 Eudora Internet Mail Server/1.2b2
        1 Eudora Internet Mail Server/2.0b10
  Exim:
       13 Exim/1.73
        5 Exim/1.651
        4 Exim/1.59
        3 Exim/1.61
        3 Exim/1.62
        2 Exim/1.70
        2 Exim/1.71
        1 Exim/ready
        1 Exim/1.73/(@HG@)
  FirstClass BBS:
        1 FirstClass BBS/1.01
  FirstClass Mail Server:
        2 FirstClass Mail Server/1.0
  GroupMaster:
        1 GroupMaster/1.4
  GroupWise:
        3 GroupWise/4.11
        1 GroupWise/5.2
  Hawkeye SMTP:
        1 Hawkeye SMTP/1.2.1
  Hummingbird SMTPD:
        1 Hummingbird SMTPD/1.0
  IBM VM SMTP:
        9 IBM VM SMTP/unknown
  IMail:
        8 IMail/4.0
        1 IMail/3.04
        1 IMail/2.1
        1 IMail/4.02
  ISOCOR:
        1 ISOCOR/1.0.242
  Integralis SMTP Receiver:
        1 Integralis SMTP Receiver/2.02
        1 Integralis SMTP Receiver/2.04
  InterLock:
        6 InterLock/3.0
  InterScan VirusWall:
        5 InterScan VirusWall/1.5++
        2 InterScan VirusWall/unknown
        1 InterScan VirusWall/2.5
  LSMTP:
        4 LSMTP/Windows NT v1.1a)
        3 LSMTP/OpenVMS v1.1a)
  LetterRip:
        3 LetterRip/unknown
  Lotus SMTP MTA:
       31 Lotus SMTP MTA/unknown
  MDaemon:
        4 MDaemon/2.6
        1 MDaemon/2.5
  MMDF:
       13 MMDF/unknown
  MS Exchange:
       26 MS Exchange/5.0.1458.49
       16 MS Exchange/5.0.1457.7
        1 MS Exchange/5.0.1459.27
        1 MS Exchange/5.5.1939.0)
  MS Mail SMTP Gateway:
        1 MS Mail SMTP Gateway/Version
  MS SMTP Mail:
       15 MS SMTP Mail/unknown
  MX:
        1 MX/4.2
  Mail.Hub TurboSendmail:
       10 Mail.Hub TurboSendmail/unknown
  Mail.Link:
        1 Mail.Link/3.0.2
  MailSite SMTP Receiver:
        3 MailSite SMTP Receiver/1.2.2
        1 MailSite SMTP Receiver/2.1.2
  Major BBS:
        1 Major BBS/2.20-2
        1 Major BBS/2.20-5
  Mercur:
        9 Mercur/2.10
  Mercury:
       13 Mercury/1.21
       10 Mercury/1.31
        6 Mercury/1.32
        4 Mercury/1.13
        4 Mercury/1.30
        3 Mercury/unknown
        2 Mercury/1.20
        2 Mercury/2.01
        1 Mercury/1.12
  NASTA Gate SMTP Server:
        1 NASTA Gate SMTP Server/1.18
  NT Mail:
       18 NT Mail/3.03.0013/1.aabv/SP
       17 NT Mail/3.02.13/1.aeuk
       10 NT Mail/3.02.13/76.b3qb
        4 NT Mail/3.02.13/1.aef3
        3 NT Mail/3.02.13/4c.ablj
        2 NT Mail/3.03.0006/16.aaaj/SP
        2 NT Mail/3.02.13/1.ac15
        2 NT Mail/3.03.0004/1.aizr/SP
        2 NT Mail/3.02.07/1.aco5
        2 NT Mail/3.02.10/1.abze
        2 NT Mail/3.02.13/1.ahyj
        2 NT Mail/3.02.13/1.af1s
        2 NT Mail/3.02.13/1.aebn
        2 NT Mail/3.02.10/1.adye
        1 NT Mail/3.02.10/1.agyg
        1 NT Mail/3.02.13/4c.aa5r
        1 NT Mail/3.02.13/17.aadg
        1 NT Mail/3.02.13/1.aibi
        1 NT Mail/3.02.13/1.ac1i
        1 NT Mail/3.02.10/43.aaaf
        1 NT Mail/3.02.13/27.aaae
        1 NT Mail/3.02.13/1.acc2
        1 NT Mail/3.03.0006/4c.abpt/SP
        1 NT Mail/3.02.13/1a.aaeg
        1 NT Mail/3.03.0012/4c.adjo/SP
        1 NT Mail/3.02.13/16.aaad
        1 NT Mail/3.02.13/16.aabf
        1 NT Mail/3.02.13/1.aazw
        1 NT Mail/3.02.10/1.aclg
        1 NT Mail/3.02.10/
        1 NT Mail/3.02.13/1c.aaas
        1 NT Mail/3.02.11/
        1 NT Mail/3.02.13/1.adfu
        1 NT Mail/3.02.08/1.afip
        1 NT Mail/3.02.13/7.aklr
  Netscape Mail server:
       52 Netscape Mail server/2.02
       15 Netscape Mail server/2.0
       13 Netscape Mail server/1.1
        8 Netscape Mail server/3.01)
        3 Netscape Mail server/2.01
        2 Netscape Mail server/3.0)
  PMDF:
       10 PMDF/5.1-8
        4 PMDF/5.1-10
        3 PMDF/5.0-8
        3 PMDF/4.3-7
        2 PMDF/5.1-7
        1 PMDF/5.0-4
        1 PMDF/5.0-5
        1 PMDF/5.0-6
        1 PMDF/5.0-7
        1 PMDF/4.2-13
        1 PMDF/4.2-15
        1 PMDF/4.3-10
  PP:
       16 PP/131
       12 PP/unknown
        7 PP/130
        6 PP/8.3
        4 PP/8.1
        4 PP/121
        2 PP/101
        1 PP/122
  Post.Office:
       52 Post.Office/3.1
       19 Post.Office/2.0
       16 Post.Office/3.1.2
        3 Post.Office/1.9.3
        2 Post.Office/3.0
        1 Post.Office/1.9.3b
        1 Post.Office/1.9.1
  PowerWeb:
        2 PowerWeb/4.03r5)
        1 PowerWeb/4.02r9)
  Raptor Firewall:
        5 Raptor Firewall/unknown
  SLMail:
        7 SLMail/2.5
        1 SLMail/2.2
  Sendmail:
      622 Sendmail/8.8.5
      345 Sendmail/8.8.7
      253 Sendmail/8.8.6
      106 Sendmail/8.7.5
       79 Sendmail/SMI-8.6
       73 Sendmail/8.8.4
       72 Sendmail/8.6.12
       63 Sendmail/8.8.3
       44 Sendmail/8.8.8
       25 Sendmail/8.7.6
       23 Sendmail/5.64
       18 Sendmail/unknown
       17 Sendmail/5.65v3.2
       17 Sendmail/5.65
       13 Sendmail/4.1
       13 Sendmail/950413.SGI.8.6.12
       12 Sendmail/8.6.11
       11 Sendmail/8.7.4
       10 Sendmail/ready
       10 Sendmail/8.7.1
        9 Sendmail/8.7.3
        8 Sendmail/8.8.4+2.7Wbeta4
        8 Sendmail/5.x
        8 Sendmail/8.8.2
        7 Sendmail/1.39.111.2/16.2
        7 Sendmail/8.6.8.1
        7 Sendmail/2.0
        7 Sendmail/8.8.7+2.7Wbeta7
        6 Sendmail/AIX4.2/UCB
        6 Sendmail/8.6.9
        5 Sendmail/5.0
        5 Sendmail/8.7
        5 Sendmail/8.8.5;
        4 Sendmail/1.38.193.4/16.2
        4 Sendmail/8.6.10
        4 Sendmail/940816.SGI.8.6.9
        4 Sendmail/8.7.2
        4 Sendmail/8.8.7-s-4
        4 Sendmail/8.8.0
        3 Sendmail/smap
        3 Sendmail/1.37.109.4/16.2
        3 Sendmail/is
        3 Sendmail/8.7.5/UNX
        3 Sendmail/5.61c:012
        2 Sendmail/5.67+1.6W
        2 Sendmail/951211.SGI.8.6.12.PATCH1502
        2 Sendmail/8.7.5.R.ML.S
        2 Sendmail/8.8.6-r-beta
        2 Sendmail/8.7.5+Spin
        2 Sendmail/8.8.5/1.4
        2 Sendmail/Grolier
        2 Sendmail/5.57
        2 Sendmail/1.37.109.16
        2 Sendmail/8.8.8+Sun.Beta.1
        2 Sendmail/8.8.5-r-beta
        2 Sendmail/8.8.7.Beta2
        2 Sendmail/8.8.1
        1 Sendmail/1.37.109.4/BelWue-1.1HP+
        1 Sendmail/-
        1 Sendmail/5.65v3.0
        1 Sendmail/1.37.109.24/16.2
        1 Sendmail/8.6.12H1
        1 Sendmail/IBM
        1 Sendmail/8.6.5.Beta9
        1 Sendmail/8.8.3+Spin
        1 Sendmail/8.6.12h2
        1 Sendmail/5.65v4.0
        1 Sendmail/NX5.67c
        1 Sendmail/8.8.5-MVC-230497
        1 Sendmail/NX5.67e
        1 Sendmail/8.6.13
        1 Sendmail/cf v2.9t-netlib
        1 Sendmail/1.37.109.16/16.2
        1 Sendmail/8.7.5-M
        1 Sendmail/1.37.109.4/15.6
        1 Sendmail/5.65a
        1 Sendmail/8.8.6.Beta0
        1 Sendmail/1.37.109.10G/16.2
        1 Sendmail/1.00
        1 Sendmail/8.6.8.2
        1 Sendmail/8.8.8+2.7Wbeta7
        1 Sendmail/$Revision: 1.37.109.26 $/15.6
        1 Sendmail/1.37.109.17/16.2
        1 Sendmail/8.8.5+2.7Wbeta5
        1 Sendmail/1.37.109.14/16.2
        1 Sendmail/8.6.4
        1 Sendmail/8.6.8
        1 Sendmail/8.6.12+2.4W
        1 Sendmail/951211.SGI.8.6.12.PATCH1042
        1 Sendmail/8.6.11+hangul
        1 Sendmail/1.37.109.23/16.2
        1 Sendmail/5.61c:013.2
        1 Sendmail/version suppressed
        1 Sendmail/8.8.8 (teergrube)
        1 Sendmail/1.37.109.24/15.6
        1 Sendmail/1.37.109.18/16.2
        1 Sendmail/950911.SGI.8.6.12.PATCH825
        1 Sendmail/ready.
        1 Sendmail/15.11/15.6
        1 Sendmail/CONVEX
  Smail:
       26 Smail/3.2
       22 Smail/unknown
       17 Smail/3.1.29.1
       14 Smail/3.1.28.1
        5 Smail/3.2.0.94
        5 Smail/3.2.0.95
        5 Smail/3.2.0.96
        3 Smail/3.2.0.91
        2 Smail/3.1.29.0
        2 Smail/3.2.0.97
        1 Smail/3.2.0.92
        1 Smail/3.2.0.98
  Soft-Switch LMS:
        1 Soft-Switch LMS/2.1.0.0
        1 Soft-Switch LMS/2.0
  TFS Gateway:
        2 TFS Gateway/2.23
        2 TFS Gateway/3.0
        1 TFS Gateway/2.21
  TGV/MultiNet, now cisco:
        1 TGV/MultiNet, now cisco/3.3
        1 TGV/MultiNet, now cisco/unknown
  UCX:
        3 UCX/4.1-12D,
        1 UCX/3.1
        1 UCX/3.3
  Worldgroup:
        1 Worldgroup/unknown
  Wrapper, maybe for Smail: Who are you gonna pretend to be today? 
        7 Wrapper, maybe for Smail/unknown
  ZMailer:
        9 ZMailer/Secure Computing
        8 ZMailer/Hotmail
        4 ZMailer/2.99.49p8
        3 ZMailer/Border Border is now secure Computing 
        1 ZMailer/2.99.48
        1 ZMailer/2.99.49p2
        1 ZMailer/2.99.49p4
        1 ZMailer/2.99.49p6a2
        1 ZMailer/2.99.49p6a7
  iSMTP:
        1 iSMTP/4.10.130
  qmail:
       74 qmail/unknown
  unknown:
       40 unknown/unknown

SMTP Extensions:

second field: absolute number of supporting servers
last two fields: percentage of all servers resp. EHLO supporting servers

  8BITMIME      1843 (61.68, 69.44)
  BINARYMIME       1 ( 0.03,  0.03)
  CHUNKING        10 ( 0.33,  0.37)
  DSN           1525 (51.03, 57.46)
  ENHANCEDSTATUSCODES  
                  26 ( 0.87,  0.97)
  ETRN          1566 (52.40, 59.00)
  EXPN          1809 (60.54, 68.16)
  HELP          2479 (82.96, 93.40)
  ONEX          1670 (55.89, 62.92)
  PIPELINING     422 (14.12, 15.90)
  SAML            34 ( 1.13,  1.28)
  SEND            34 ( 1.13,  1.28)
  SIZE          2316 (77.51, 87.26)
  SOML            34 ( 1.13,  1.28)
  TIME            16 ( 0.53,  0.60)
  TLS              1 ( 0.03,  0.03)
  TURN            23 ( 0.76,  0.86)
  VERB          1238 (41.43, 46.64)
  VRFY           175 ( 5.85,  6.59)
  XADR            29 ( 0.97,  1.09)
  XAUD            24 ( 0.80,  0.90)
  XAUTH           43 ( 1.43,  1.62)
  XDATASIZE        7 ( 0.23,  0.26)
  XEXCH50         44 ( 1.47,  1.65)
  XGEN            16 ( 0.53,  0.60)
  XONE            18 ( 0.60,  0.67)
  XQUE            18 ( 0.60,  0.67)
  XREMOTEQUEUE   177 ( 5.92,  6.66)
  XSTA            27 ( 0.90,  1.01)
  XTRN             7 ( 0.23,  0.26)
  XUSR          1486 (49.73, 55.99)
  XVRB            18 ( 0.60,  0.67)

alphabetical sorted software list with SMTP extensions:

  Advox Omnigate 
                8BITMIME, ETRN
  Apple Internet Mail Server  
                EXPN, PIPELINING, SIZE
  Connect2-SMTP 8BITMIME, EXPN, HELP
  Eudora Internet Mail Server  
                BINARYMIME, CHUNKING, ENHANCEDSTATUSCODES, ETRN, EXPN
                PIPELINING, SIZE
  Exim          ETRN, EXPN, HELP, SIZE
  IMail         ETRN, EXPN, SIZE
  ISOCOR        8BITMIME, DSN, ETRN, EXPN, HELP, PIPELINING, SIZE
  Integralis SMTP Receiver  
                8BITMIME, SIZE
  InterScan VirusWall  
                8BITMIME, DSN, ETRN, EXPN, HELP, ONEX, SIZE, VERB, XUSR
  LSMTP         8BITMIME, HELP, PIPELINING, XDATASIZE
  MDaemon       EXPN, VRFY
  MS Exchange   DSN, ETRN, HELP, SIZE, TLS, VRFY, XAUTH, XEXCH50
  MS SMTP Mail  PIPELINING, SIZE
  Mail.Hub TurboSendmail  
                8BITMIME, DSN, EXPN, PIPELINING, SIZE
  MailSite SMTP Receiver  
                8BITMIME, ETRN, SIZE
  Mercur        EXPN, HELP, SIZE
  Mercury       8BITMIME, HELP, SIZE, TIME
  NT Mail       HELP, VRFY, XAUD
  Netscape Mail server  
                DSN, ETRN, EXPN, HELP, PIPELINING, XREMOTEQUEUE
  PMDF          8BITMIME, DSN, ENHANCEDSTATUSCODES, ETRN, EXPN, HELP
                PIPELINING, SAML, SEND, SIZE, SOML, TURN, XADR, XGEN
                XSTA
  PP            HELP, SIZE, VRFY
  Post.Office   EXPN, HELP, PIPELINING, SIZE, XREMOTEQUEUE
  SLMail        ETRN, EXPN, HELP, SAML, SEND, SIZE, SOML, XTRN
  Sendmail      8BITMIME, DSN, ETRN, EXPN, HELP, ONEX, SIZE, VERB, XONE
                XQUE, XUSR, XVRB
  Smail         8BITMIME, EXPN, HELP, PIPELINING, SIZE
  ZMailer       8BITMIME, CHUNKING, DSN, ENHANCEDSTATUSCODES, ETRN
                EXPN, HELP, PIPELINING, SIZE, VRFY
  qmail         8BITMIME, PIPELINING
  unknown       8BITMIME, DSN, ETRN, EXPN, HELP, ONEX, PIPELINING, SIZE
                XUSR

alphabetical list of smtp extension with supporting software:

  8BITMIME      Advox Omnigate, Connect2-SMTP, ISOCOR
                Integralis SMTP Receiver, InterScan VirusWall, LSMTP
                Mail.Hub TurboSendmail, MailSite SMTP Receiver, Mercury
                PMDF, Sendmail, Smail, ZMailer, unknown, qmail
  BINARYMIME    Eudora Internet Mail Server
  CHUNKING      Eudora Internet Mail Server, ZMailer
  DSN           ISOCOR, InterScan VirusWall, MS Exchange
                Mail.Hub TurboSendmail, Netscape Mail server, PMDF
                ZMailer, unknown, Sendmail
  ENHANCEDSTATUSCODES  
                Eudora Internet Mail Server, PMDF, ZMailer
  ETRN          Advox Omnigate, Eudora Internet Mail Server, Exim
                IMail, ISOCOR, InterScan VirusWall, MS Exchange
                MailSite SMTP Receiver, Netscape Mail server, PMDF
                SLMail, ZMailer, unknown, Sendmail
  EXPN          Apple Internet Mail Server, Connect2-SMTP
                Eudora Internet Mail Server, Exim, IMail, ISOCOR
                InterScan VirusWall, MDaemon, Mail.Hub TurboSendmail
                Mercur, Netscape Mail server, PMDF, Post.Office, SLMail
                Smail, ZMailer, unknown, Sendmail
  HELP          Connect2-SMTP, Exim, ISOCOR, InterScan VirusWall, LSMTP
                MS Exchange, Mercury, NT Mail, Netscape Mail server
                PMDF, PP, Post.Office, SLMail, Smail, ZMailer, unknown
                Sendmail
  ONEX          InterScan VirusWall, unknown, Sendmail
  PIPELINING    Apple Internet Mail Server, Eudora Internet Mail Server
                ISOCOR, LSMTP, MS SMTP Mail, Mail.Hub TurboSendmail
                Netscape Mail server, PMDF, Post.Office, Smail, ZMailer
                unknown, qmail
  SAML          SLMail, PMDF
  SEND          SLMail, PMDF
  SIZE          Apple Internet Mail Server, Eudora Internet Mail Server
                Exim, IMail, ISOCOR, Integralis SMTP Receiver
                InterScan VirusWall, MS Exchange, MS SMTP Mail
                Mail.Hub TurboSendmail, MailSite SMTP Receiver, Mercury
                PMDF, PP, Post.Office, SLMail, Smail, ZMailer, unknown
                Sendmail
  SOML          SLMail, PMDF
  TIME          Mercury
  TLS           MS Exchange
  TURN          PMDF
  VERB          InterScan VirusWall, Sendmail
  VRFY          MDaemon, MS Exchange, NT Mail, PP, ZMailer
  XADR          PMDF
  XAUD          NT Mail
  XAUTH         MS Exchange
  XDATASIZE     LSMTP
  XEXCH50       MS Exchange
  XGEN          PMDF
  XONE          Sendmail
  XQUE          Sendmail
  XREMOTEQUEUE  Post.Office, Netscape Mail server
  XSTA          PMDF
  XTRN          SLMail
  XUSR          InterScan VirusWall, unknown, Sendmail
  XVRB          Sendmail

as we all know: there are lies, damn lies and statistics. So take this with a grain of salt.