从我的Linux服务器发送垃圾邮件

有人可以建议我如何阻止从我的Linux服务器发送的所有电子邮件.
如果有帮助的话,我在Ubuntu 12.03 LTS上.

Jan 31 09:52:30 myserver postfix/smtp[55852]: 03EC14869A: to=<QAnne-Pascale.Targe@ciera.ulaval.ca>,relay=exch-spam02.ulaval.ca[132.203.244.24]:25,delay=229193,delays=229193/0.17/0.47/0,dsn=4.0.0,status=deferred (host exch-spam02.ulaval.ca[132.203.244.24] refused to talk to me: 554-exch-spam02.ulaval.ca 554 Your access to this mail system has been rejected due to the sending MTA's poor reputation. If you believe that this failure is in error,please contact the intended recipient via alternate means.)
Jan 31 09:52:30 myserver postfix/smtp[55870]: connect to cluster8.us.messagelabs.com[216.82.241.132]:25: Connection refused
Jan 31 09:52:30 myserver postfix/smtp[55849]: 5049348710: to=<Qst-onge.mathieu.3@courrier.uqam.ca>,relay=mail3.uqam.ca[132.208.246.162]:25,delay=229188,delays=229187/0.15/0.52/0,status=deferred (host mail3.uqam.ca[132.208.246.162] refused to talk to me: 554-data.crochet.telecom.uqam.ca 554 Your access to this mail system has been rejected due to the sending MTA's poor reputation. If you believe that this failure is in error,please contact the intended recipient via alternate means.)
Jan 31 09:52:30 myserver postfix/smtp[55870]: connect to cluster8a.us.messagelabs.com[85.158.139.103]:25: Connection refused
Jan 31 09:52:30 myserver postfix/smtp[55861]: 3437C4876E: to=<racicot.yves@uqam.ca>,delay=229181,delays=229180/0.2/0.45/0,please contact the intended recipient via alternate means.)
Jan 31 09:52:30 myserver postfix/smtp[55846]: 8503348BF7: to=<tremblayjg@csc-scc.gc.ca>,relay=mail2.csc-scc.gc.ca[198.103.56.136]:25,delay=228588,delays=228587/0.12/0.68/0,status=deferred (host mail2.csc-scc.gc.ca[198.103.56.136] refused to talk to me: 554-mxlaval.csc-scc.gc.ca 554 Your access to this mail system has been rejected due to the sending MTA's poor reputation. If you believe that this failure is in error,please contact the intended recipient via alternate means.)
Jan 31 09:52:30 myserver postfix/smtp[55870]: connect to cluster8a.us.messagelabs.com[216.82.251.230]:25: Connection refused
Jan 31 09:52:30 myserver postfix/smtp[55865]: A5E364984A: to=<vaillancourt.yves@uqam.ca>,relay=mail2.uqam.ca[132.208.246.165]:25,delay=228559,delays=228558/0.27/0.46/0,status=deferred (host mail2.uqam.ca[132.208.246.165] refused to talk to me: 554-data.hamecon.telecom.uqam.ca 554 Your access to this mail system has been rejected due to the sending MTA's poor reputation. If you believe that this failure is in error,please contact the intended recipient via alternate means.)
Jan 31 09:52:30 myserver postfix/smtp[55870]: F0E6948932: to=<rbrophy@bickertonbrokers.com>,relay=none,delay=229161,delays=229161/0.33/0.4/0,dsn=4.4.1,status=deferred (connect to cluster8a.us.messagelabs.com[216.82.251.230]:25: Connection refused)
Jan 31 09:52:30 myserver postfix/smtp[55843]: A83CA486EF: to=<Qjonathan.durand-folcol.1@ulaval.ca>,delay=229191,delays=229190/0.27/0.48/0,please contact the intended recipient via alternate means.)
Jan 31 09:52:30 myserver postfix/smtp[55845]: 2E49B4866E: host mx11.exchange.telus.com[205.206.208.34] refused to talk to me: 554-mx21.exchange.telus.com 554 Your access to this mail system has been rejected due to the sending MTA's poor reputation. If you believe that this failure is in error,please contact the intended recipient via alternate means.
Jan 31 09:52:30 myserver postfix/smtp[55856]: 12A4A4DF0A: to=<Ipoussons-poussettes@bellnet.ca>,relay=mxmta.bellnet.ca[67.69.240.61]:25,delay=231626,delays=231625/0.17/0.92/0,dsn=4.4.2,status=deferred (lost connection with mxmta.bellnet.ca[67.69.240.61] while receiving the initial server greeting)
Jan 31 09:52:30 myserver postfix/smtp[55845]: 2E49B4866E: host mx12.exchange.telus.com[205.206.208.35] refused to talk to me: 554-mx22.exchange.telus.com 554 Your access to this mail system has been rejected due to the sending MTA's poor reputation. If you believe that this failure is in error,please contact the intended recipient via alternate means.
Jan 31 09:52:30 myserver postfix/smtp[55850]: 53A1948A8C: to=<Troy@ExitInTheSoo.com>,relay=presmtp.ex1.secureserver.net[72.167.238.201]:25,delay=228581,delays=228579/0.15/1.2/0,status=deferred (host presmtp.ex1.secureserver.net[72.167.238.201] refused to talk to me: 554-p3pismtp01-057.prod.phx3.secureserver.net 554 Your access to this mail system has been rejected due to the sending MTA's poor reputation. If you believe that this failure is in error,please contact the intended recipient via alternate means.)
Jan 31 09:52:31 myserver postfix/smtp[55844]: 955704945F: to=<tpeddigrew@cogeco.ca>,relay=MX.cogeco.ca[216.221.81.26]:25,delay=228598,delays=228596/0.1/1.4/0,status=deferred (lost connection with MX.cogeco.ca[216.221.81.26] while receiving the initial server greeting)
Jan 31 09:52:31 myserver postfix/smtp[55845]: 2E49B4866E: host mx13.exchange.telus.com[209.171.64.82] refused to talk to me: 554-mx24.exchange.telus.com 554 Your access to this mail system has been rejected due to the sending MTA's poor reputation. If you believe that this failure is in error,please contact the intended recipient via alternate means.
Jan 31 09:52:31 myserver postfix/smtp[55845]: 2E49B4866E: to=<pwong@williamsengineering.com>,relay=mx14.exchange.telus.com[209.171.64.83]:25,delay=229196,delays=229194/0.1/1.6/0,status=deferred (host mx14.exchange.telus.com[209.171.64.83] refused to talk to me: 554-mx25.exchange.telus.com 554 Your access to this mail system has been rejected due to the sending MTA's poor reputation. If you believe that this failure is in error,please contact the intended recipient via alternate means.)
Jan 31 09:52:31 myserver postfix/smtp[55862]: 343EB486F0: to=<Qnicolas_gignac@inrs-ete.uquebec.ca>,delay=229190,delays=229188/0.21/1.5/0,dsn=4.4.3,status=deferred (Host or domain name not found. Name service error for name=inrs-ete.uquebec.ca type=MX: Host not found,try again)
Jan 31 09:52:33 myserver postfix/smtp[55847]: 611C348731: to=<query@coastalwinds.com>,delay=229189,delays=229185/0.13/3.3/0,status=deferred (Host or domain name not found. Name service error for name=coastalwinds.com type=MX: Host not found,try again)
Jan 31 09:52:33 myserver postfix/smtp[55848]: 6146948685: to=<Qfoisy.catherine.2@courrier.uqam.ca>,delay=229195,delays=229191/0.14/3.5/0,please contact the intended recipient via alternate means.)
Jan 31 09:52:59 myserver postfix/smtp[55854]: connect to gmail.co[173.194.34.182]:25: Connection timed out
Jan 31 09:52:59 myserver postfix/smtp[55860]: connect to hortmail.com[65.55.39.10]:25: Connection timed out
Jan 31 09:52:59 myserver postfix/smtp[55855]: connect to saskpower.ca[65.39.140.84]:25: Connection timed out
Jan 31 09:52:59 myserver postfix/smtp[55855]: 022C148CCF: to=<rgin@saskpower.ca>,delay=229153,delays=229123/0.15/30/0,status=deferred (connect to saskpower.ca[65.39.140.84]:25: Connection timed out)
Jan 31 09:53:00 myserver postfix/smtp[55866]: connect to remax-lethbridge.com[208.91.196.163]:25: Connection timed out
Jan 31 09:53:00 myserver postfix/smtp[55866]: B370A48B44: to=<remax@remax-lethbridge.com>,delay=229168,delays=229137/0.28/30/0,status=deferred (connect to remax-lethbridge.com[208.91.196.163]:25: Connection timed out)
Jan 31 09:53:29 myserver postfix/smtp[55854]: connect to gmail.co[173.194.34.181]:25: Connection timed out
Jan 31 09:53:29 myserver postfix/smtp[55854]: 056994B723: to=<Wesleyscott99@gmail.co>,delay=228541,delays=228481/0.19/60/0,status=deferred (connect to gmail.co[173.194.34.181]:25: Connection timed out)
Jan 31 09:53:29 myserver postfix/smtp[55860]: connect to hortmail.com[64.4.6.100]:25: Connection timed out
Jan 31 09:53:29 myserver postfix/smtp[55860]: 3F3DE48F58: to=<rmaliaa@hortmail.com>,delay=229137,delays=229076/0.19/60/0,status=deferred (connect to hortmail.com[64.4.6.100]:25: Connection timed out)