(PowerShell) IMAP Download and Verify Signed MIME

Downloads the unmodified MIME of a digitally signed email, saves the .p7s signature (and other MIME parts), then loads the email into a Chilkat email object (which unwraps the S/MIME and verifies the signature) and then saves attachments (if the MIME parts were not already saved).

Chilkat .NET Downloads Chilkat .NET Assemblies

Add-Type -Path "C:\chilkat\ChilkatDotNet47-9.5.0-x64\ChilkatDotNet47.dll"

# This example requires the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

$imap = New-Object Chilkat.Imap

# Connect to an IMAP server.
# Use TLS
$imap.Ssl = $true
$imap.Port = 993
$success = $imap.Connect("imap.someMailServer.com")
if ($success -ne $true) {
    $($imap.LastErrorText)
    exit
}

$success = $imap.Login("myLogin","myPassword")
if ($success -ne $true) {
    $($imap.LastErrorText)
    exit
}

# Select an IMAP mailbox
$success = $imap.SelectMailbox("Inbox")
if ($success -ne $true) {
    $($imap.LastErrorText)
    exit
}

# Download the 1st email (as MIME) in the Inbox by sequence number.
$sbMime = New-Object Chilkat.StringBuilder
$success = $imap.FetchSingleAsMimeSb(1,$false,$sbMime)
if ($success -ne $true) {
    $($imap.LastErrorText)
    exit
}

# Load it into a MIME object and check to see if it is signed
$mime = New-Object Chilkat.Mime
$mime.LoadMimeSb($sbMime)
$alreadySavedParts = $false
if ($mime.ContainsSignedParts() -eq $true) {

    # This will save the .p7s and other parts...
    $sa = $mime.ExtractPartsToFiles("qa_output")
    if ($mime.LastMethodSuccess -eq $true) {
        $numFiles = $sa.Count
        $i = 0
        while ($i -lt $numFiles) {
            $("Created: " + $sa.GetString($i))
            $i = $i + 1
        }

        $alreadySavedParts = $true
    }

}

# Load the MIME into an Email object.  This unwraps the security layers and verifies signatures.
$email = New-Object Chilkat.Email
$email.SetFromMimeSb($sbMime)

if ($email.ReceivedSigned -eq $true) {

    $("This email was signed.")

    # Check to see if the signatures were verified.
    if ($email.SignaturesValid -eq $true) {
        $("Digital signature(s) verified.")

        $("Signer: " + $email.SignedBy)

        # The certificate used for signing may be obtained
        # by calling email.GetSignedByCert.
        $cert = $email.GetSignedByCert()
        if ($email.LastMethodSuccess -ne $true) {
            $("Failed to get signing certificate object.")
        }
        else {
            $("Signing cert: " + $cert.SubjectCN)

        }

    }

}
else {
    $("Digital signature verification failed.")
}

if ($alreadySavedParts -ne $true) {
    $email.SaveAllAttachments("qa_output")
}