PowerShell

Load .eml and Decrypt (smime.p7m)

Loads an encrypted email from a .eml file and decrypts using certificate w/ private key found in a .p12 (or .pfx) file.

The Content-Type and Content-Disposition email headers of the email to be decrypted look similar to this:

Content-Type: application/x-pkcs7-mime; smime-type=enveloped-data;
	name="smime.p7m"
Content-Disposition: attachment; filename="smime.p7m"

PowerShell

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

$success = $false

$email = New-Object Chilkat.Email

# Add a PFX (or .p12) to be used for decryption
$success = $email.AddPfxSourceFile("myCert.p12","passwordForP12")
if ($success -ne $true) {
    $($email.LastErrorText)
    exit
}

# Loading the .eml automatically decrypts.
$success = $email.LoadEml("encrypted.eml")
if ($success -ne $true) {
    $($email.LastErrorText)
    exit
}

# The email now exists as it was prior to encryption.
# Your app may access the email's subject, body, attachments,
# etc. using the Chilkat Email API...

# Save the decrypted email:
$success = $email.SaveEml("decrypted.eml")
if ($success -ne $true) {
    $($email.LastErrorText)
    exit
}

$("Success.")