查询邮件是否已读：
$Sender = "a@test.com"
$Recipients = "b@test.com"
$Subject = "主题"
$msg = Search-MessageTrackingReport -Identity $Sender -Subject $Subject -Recipients $Recipients -BypassDelegateChecking | %{Get-MessageTrackingReport -Identity($_.MessageTrackingReportId) -BypassDelegateChecking -RecipientPathFilter $Recipients -ReportTemplate recipientpath}
$msg.RecipientTrackingEvents