How to inspect spam logs in Exchange Server 2010

Open an Exchange Management Shell on Edge Transport Server and use Get-AgentLog command to examine the logs:
Get-AgentLog -StartDate "01/01/2012 0:00:00" -EndDate "02/01/2012 23:59:59" | ? {$_.IPAddress -eq "a.b.c.d"} | more
Get-AgentLog -StartDate "01/01/2012 0:00:00" -EndDate "02/01/2012 23:59:59" | ? {$_.SmtpResponse -like "*5.1.1*"} | more