Please help me analyse the log

I am vwry new in postfix and even linux.

Begun from 2/2/2004 the following similar logs appear on my server. The sources were vary and the mails were tried to send to random user in my doamin (eg. Mary,Brain, etc). I want to know what was happening. I was afraid if my server being hacked, became an open relay server or if other server block emails from my servers.

Feb 2 18:07:26 www postfix/smtpd[9059]: connect from unknown[221.124.98.96]
Feb 2 18:07:26 www postfix/smtpd[9059]: 0E61037742: client=unknown[221.124.98.96]
Feb 2 18:07:26 www postfix/cleanup[9062]: 0E61037742: message-id=<20040202100726.0E61037742@www.foo.com>
Feb 2 18:07:26 www postfix/nqmgr[18634]: 0E61037742: from=<ray@kuririnmail.com>, size=31996, nrcpt=1 (queue active)
Feb 2 18:07:26 www postfix/smtpd[9059]: disconnect from unknown[221.124.98.96]
Feb 2 18:07:26 www postfix/local[9063]: 0E61037742: to=<mary@www.foo.com>, relay=local, delay=0, status=bounced (unknown user: "mary")
Feb 2 18:07:26 www postfix/cleanup[9062]: 1BC2C3774A: message-id=<20040202100726.1BC2C3774A@www.foo.com>
Feb 2 18:07:26 www postfix/nqmgr[18634]: 1BC2C3774A: from=<>, size=33520, nrcpt=1 (queue active)
Feb 2 18:07:46 www postfix/smtpd[9059]: connect from unknown[221.124.98.96]
Feb 2 18:07:46 www postfix/smtpd[9059]: 9D07E37742: client=unknown[221.124.98.96]
Feb 2 18:07:46 www postfix/cleanup[9062]: 9D07E37742: message-id=<20040202100746.9D07E37742@www.foo.com>
Feb 2 18:07:46 www postfix/smtpd[9059]: disconnect from unknown[221.124.98.96]
Feb 2 18:07:46 www postfix/nqmgr[18634]: 9D07E37742: from=<sandra@hellokitty.com>, size=32198, nrcpt=1 (queue active)
Feb 2 18:07:46 www postfix/local[9063]: 9D07E37742: to=<jose@www.foo.com>, relay=local, delay=0, status=bounced (unknown user: "jose")
Feb 2 18:07:46 www postfix/cleanup[9062]: B14DC3774B: message-id=<20040202100746.B14DC3774B@www.foo.com>
Feb 2 18:07:46 www postfix/nqmgr[18634]: B14DC3774B: from=<>, size=33724, nrcpt=1 (queue active)
Feb 2 18:08:26 www postfix/smtp[9066]: B14DC3774B: to=<sandra@hellokitty.com>, relay=hellokitty-com.mr.outblaze.com[205.158.62.52], delay=40, status=bounced (host hellokitty-com.mr.outblaze.com[205.158.62.52] said: 550 Error: Bounce likely due to MyDoom. Not wanted.)
Feb 2 18:08:59 www postfix/smtp[9065]: 1BC2C3774A: to=<ray@kuririnmail.com>, relay=kuririnmail-com.mr.outblaze.com[205.158.62.52], delay=93, status=bounced (host kuririnmail-com.mr.outblaze.com[205.158.62.52] said: 550 Error: Bounce likely due to MyDoom. Not wanted.)

Feb 6 15:11:05 www postfix/smtpd[27786]: connect from 061093215162.ctinets.com[61.93.215.162]
Feb 6 15:11:05 www postfix/smtpd[27786]: 7037037742: client=061093215162.ctinets.com[61.93.215.162]
Feb 6 15:11:05 www postfix/cleanup[27787]: 7037037742: message-id=<20040206071105.7037037742@www.olc.edu.hk>
Feb 6 15:11:05 www postfix/nqmgr[18634]: 7037037742: from=<dave@staff.sina.com>, size=32143, nrcpt=1 (queue active)
Feb 6 15:11:05 www postfix/local[27788]: 7037037742: to=<matt@www.olc.edu.hk>, relay=local, delay=0, status=bounced (unknown user: "matt")
Feb 6 15:11:05 www postfix/cleanup[27787]: AEB813774D: message-id=<20040206071105.AEB813774D@www.olc.edu.hk>
Feb 6 15:11:05 www postfix/nqmgr[18634]: AEB813774D: from=<>, size=33667, nrcpt=1 (queue active)
Feb 6 15:11:05 www postfix/smtpd[27786]: disconnect from 061093215162.ctinets.com[61.93.215.162]
Feb 6 15:11:29 www postfix/smtp[27790]: AEB813774D: to=<dave@staff.sina.com>, relay=mx2.sina.net[202.108.37.52], delay=24, status=bounced (host mx2.sina.net[202.108.37.52] said: 550 ???????? - invalid address (#5.5.0))
Feb 6 15:13:37 www postfix/smtpd[27792]: connect from 061093215162.ctinets.com[61.93.215.162]
Feb 6 15:13:37 www postfix/smtpd[27792]: 2361F37742: client=061093215162.ctinets.com[61.93.215.162]
Feb 6 15:13:37 www postfix/cleanup[27793]: 2361F37742: message-id=<20040206071337.2361F37742@www.olc.edu.hk>
Feb 6 15:13:37 www postfix/nqmgr[18634]: 2361F37742: from=<sandra@sinaman.com>, size=32852, nrcpt=1 (queue active)
Feb 6 15:13:37 www postfix/local[27794]: 2361F37742: to=<alice@www.olc.edu.hk>, relay=local, delay=0, status=bounced (unknown user: "alice")
Feb 6 15:13:37 www postfix/cleanup[27793]: 7C5AC3774D: message-id=<20040206071337.7C5AC3774D@www.olc.edu.hk>
Feb 6 15:13:37 www postfix/nqmgr[18634]: 7C5AC3774D: from=<>, size=34379, nrcpt=1 (queue active)
Feb 6 15:13:37 www postfix/smtpd[27792]: disconnect from 061093215162.ctinets.com[61.93.215.162]
Feb 6 15:13:52 www postfix/smtp[27796]: 7C5AC3774D: to=<sandra@sinaman.com>, relay=sinamail1.sina.com.hk[202.85.139.200], delay=15, status=bounced (host sinamail1.sina.com.hk[202.85.139.200] said: 553 sorry, your envelope sender is in my badmailfrom list (#5.7.1))

Thanks!!
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