Powershell Exchange script returning inconsistent results – PS weirdness

Try this out (haven't run it myself):

Import-Module C:\Temp\Exchange.psm1
$filter = "(&(objectCategory=person)(objectClass=user)(userAccountControl:1.2.840.113556.1.4.803:=2))"
$users = ([adsiSearcher]$Filter).findall()
foreach($suser in $users)
    {
    if($suser.properties.item("showInAddressBook") -ne $null) {
        get-mailbox "$($suser.properties.item("sAMAccountName"))" | ? {$_.RecipientType -eq "UserMailbox"} | set-mailbox -HiddenFromAddressListsEnabled $True
    }
}

Notes:

• Run this in the Powershell ISE, not the Exchange Management Shell.
• You will need to change the "Import-Module" line at the top to point to the Exchange.psm1 file on your Exchange management machine for this to work.
• I would try just printing the user accounts that you are going to hide first to make sure it is going to affect the users you think it is before you configure their mailboxes. (Put a # before the pipe to set-mailbox to comment that part out)

Since the output formatting in the PowerShell prompt happens when you actually output $CertToList, and you're not interested in that here, you might want to construct a HTML structure to present the output in the mail message.

Update Since you want to embed an inline attachment in the form of an image, we'll have to do the work of creating and sending the email ourselves, instead of relying on Send-MailMessage:

# Smtp details as outlined by Colyn1337
$smtpServer = "server.domain.com"
$smtpFrom = "emailfrom@address.com"
$smtpTo = "emailto@address.com"
$messageSubject = "The subject line of the email"

# Set up an SmtpClient for sending the message
$smtpClient = New-Object Net.Mail.SmtpClient
$smtpClient.Host = $smtpServer

# Create the MailMessage you want to send
$mailMessage = New-Object Net.Mail.MailMessage
$mailMessage.From = $smtpFrom
$mailMessage.To.Add($smtpTo)
$mailMessage.Subject = $messageSubject

# Create the html content for the mail
# Add embedded image resource to HTML
$htmlReport  = "<image src=cid:DangeRussLogo>"

# And then the table with your data
$htmlReport += "<table>"
$htmlReport += "`n"
$htmlReport += "<tr>"
$htmlReport += "<th>RequestID</th>"
$htmlReport += "<th>RequesterName</th>"
$htmlReport += "<th>RequestType</th>"
$htmlReport += "<th>NotAfter</th>"
$htmlReport += "<th>CommonName</th>"
$htmlReport += "<th>EnrollmentFlags</th>"
$htmlReport += "</tr>"
$htmlReport += "`n"
foreach($cert in $CertToList)
{
    $htmlReport += "<tr>"
    $htmlReport += "<td>$($cert.RequestID)</td>"
    $htmlReport += "<td>$($cert.RequesterName)</td>"
    $htmlReport += "<td>$($cert.RequestType)</td>"
    $htmlReport += "<td>$($cert.NotAfter)</td>"
    $htmlReport += "<td>$($cert.CommonName)</td>"
    $htmlReport += "<td>$($cert.EnrollmentFlags)</td>"
    $htmlReport += "</tr>"
    $htmlReport += "`n"
}

$htmlReport += "</table>"

# Now create an AlternateView from the HTML contents
$messageBody = [Net.Mail.AlternateView]::CreateAlternateViewFromString($htmlReport, 'text/html')

# Create a Linked Resource from the logo image
$imageMimeType = New-Object System.Net.Mime.ContentType("image/png")
$embeddedImage = New-Object Net.Mail.LinkedResource("C:\Users\DangeRuss\logo.png", $imageMimeType)
$embeddedImage.ContentId = "DangeRussLogo"

# Add the resource to the HTML view
$messageBody.LinkedResources.Add($embeddedImage)

# Add the HTML view to the MailMessage
$mailMessage.AlternateViews.Add($messageBody)

# And finally send the message
$smtpClient.Send($mailMessage)

If you want to use a .jpeg or .jpg file instead on PNG, change the MimeType from "image/png" to "image/jpeg"