Good one liner for Exchange 2007 and 2010 to find DSN Failures. Get-MessageTrackingLog -resultsize unlimited -start "12/13/2011 3:00PM" -End "12/13/2011 6:00PM" -Server srv-hub02 | ? {$_.EventId -eq "DSN" -and $_.SourceContext -eq "Failure"} | select timestamp,recipients,messagesubject