Well not exactly dominating. Maybe not secretly either. But it sounded good. This oneliner from the department of utterly useless info tells it all:
agrep "^User-Agent: ,^X-Mailer: " user|perl -ne 'chomp;/.+?: (.?.?.?[^\d,\(,\[,\/]{1,14}).*/; $o=$1; $o=~s/ //g;print "$o\n";'|sort|uniq -dc|sort -rn 8032 Mutt 1531 Mozilla 1405 MicrosoftOutlook 944 KMail 930 Gnus 524 Evolution 261 QUALCOMMWindows 220 exmhversion 213 Balsa 211 Sylpheedversion 209 InternetMailSer 133 AOL 107 VM 67 IMP 52 TheBat! 51 Prontov 50 XFMail 50 WWW-Mail 31 Spruce 30 SquirrelMail 26 ELM 25 WebMail 25 Becky!ver. 22 NovellGroupWise 22 Mutthttp: 21 VirtualAccessby 20 Elm 17 ForteAgent 17 Edsamail 15 Microsoft-Outlook 14 tin 14 Mutt- 14 LotusNotesRelea 14 DMailWebWebtoM 14 CronosII 12 SEMI 12 GNUEmacs 11 Mewversion 10 mutt 10 mailgate 10 Unknown 9 VistoServer 9 Visto 9 PMMail 9 Mailsmith 9 KNode 9 JAWmail 8 MIME-tools 8 Gnusv 7 WindowsEudoraLi 7 Mulberry 7 MH 6 mutt-nntp 6 mPOPWeb-Mail 6 dMail 6 CalypsoVersion 5 nail 5 WindowsEudoraPr 5 TurnpikeIntegrat 5 TkMail 5 RMM 5 AtlasMailer 5 21. 5 "AlexHart'sVery 5 4 emacs 4 TWIG 4 Opera 4 MailCityService 4 EMIKO 4 AppleMail 3 Pluto 3 PHP 3 NeoMail 3 NIMSModWebModul 3 MicrosoftInterne 3 MacSOUP 3 EMUmail 3 CommuniGateProW 3 Becky!ver 2 slrn 2 dtmail 2 Webmin 2 UltrafunkPopcorn 2 Turnpike 2 SoftForum-WebMail 2 Postaci 2 PocoMail 2 Pan 2 NetscapeWebmail 2 Mailer? 2 MSNExplorer 2 Lynx 2 JMail 2 InterChange 2 InMailbyInsite 2 Gmail 2 AT&TMessageCent 2 <IMailv -- oivvio polite cell +46 (0)709 30 40 30 / phone +46 (0)8 669 64 18 / fax +46 (0)8 84 00 18 varvsgatan 10A / s-117 29 stockholm / sweden