PowerShell

Check if an Email Was Received Digitally Signed

Demonstrates the read-only Chilkat Email.ReceivedSigned property, which is true if the email was originally received carrying one or more digital signatures. Knowing a message was signed is separate from knowing the signature checked out, so this example also reads SignaturesValid to report whether the signed content verified.

Background: A digital signature on an email (S/MIME) provides two things: authenticity (it was really sent by the holder of a particular certificate) and integrity (the content was not altered in transit). The sender signs a hash of the message with their private key; the recipient verifies it with the sender's public certificate. ReceivedSigned simply tells you a signature is present — verifying it is a separate step exposed through SignaturesValid.

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

$success = $false

#  Demonstrates the read-only Email.ReceivedSigned property, which is true if this
#  email was originally received with a digital signature.  Use SignaturesValid to
#  determine whether the signed content actually verified.

$email = New-Object Chilkat.Email

$success = $email.LoadEml("qa_data/eml/signed.eml")
if ($success -eq $false) {
    $($email.LastErrorText)
    exit
}

if ($email.ReceivedSigned -eq $true) {
    $("This email was received with a digital signature.")
    if ($email.SignaturesValid -eq $true) {
        $("All signatures are valid.")
    }
    else {
        $("One or more signatures are NOT valid.")
    }

}
else {
    $("This email was not signed.")
}

#  Note: Paths such as "qa_data/..." are relative local filesystem paths,
#  relative to the current working directory of the running application.