The following vb6 codes demonstrate how to verify S/MIME digital signature and decrypt encrypted email.
How to sign email?
Digital signature is always signed by sender certificate. The certificate used to sign email content MUST have the public/private key pair.
First of all, the user MUST get a digital certificate for personal email protection from third-party certificate authorities such as www.verisign.com.
After the certificate is installed on the machine, it can be viewed by
Internet Options ->
When you view the certificate, please note there is a line “You have a private key that corresponds
to this certificate” in the certificate view, that means you are able to
use this certificate to sign email content. If this line doesn’t appear, that means
you are unable to sign the email content by this certificate.
To sign email content, please refer to EASendMail SMTP Component.
How to encrypt email?
Encrypting email doesn’t require sender certificate but the certificate with public key for every recipient.
firstname.lastname@example.org sends an email to
with digital signature; The digital signature contains the public key certificate for
email@example.com can send an encrypted email with this certificate back to
from@adminsystem can read this email, because this email MUST be decrypted by private key of
Therefore, you MUST receive an digital signed email from other people (Most email clients such as outlook, outlook express will add the certificate to the Other People Storage automatically once an digital signed email is received) before you can send encrypted email to this people.
To encrypt email, please refer to EASendMail SMTP Component.
Before you can use the following sample codes, you should download the EAGetMail Installer and install it on your machine at first. Full sample projects are included in this installer.
To use EAGetMail POP3 & IMAP4 ActiveX Object in your project,
the first step is
Add reference of EAGetMail to your project.
Please go to
References -> and select
EAGetMailObj ActiveX Object, click
the reference will be added to your project, and you can start to use it to retrieve email and parse email in your project.
The following example codes demonstrate parsing S/MIME email - digital signature and decryption.
In order to run it correctly, please change
file name value to yours.
To get full sample projects, please download and install EAGetMail on your machine.
Option Explicit Const CRYPT_MACHINE_KEYSET = 32 Const CRYPT_USER_KEYSET = 4096 Const CERT_SYSTEM_STORE_CURRENT_USER = 65536 Const CERT_SYSTEM_STORE_LOCAL_MACHINE = 131072 Private Sub ParseEmail(ByVal emlFile As String) Dim oMail As New EAGetMailObjLib.Mail oMail.LicenseCode = "TryIt" On Error GoTo ErrorHandle oMail.LoadFile emlFile, False If oMail.IsEncrypted Then ' This email is encrypted, we decrypt it by user default certificate. ' You can also use specified certificate like this ' Dim oCert As New EAGetMailObjLib.Certificate ' oCert.LoadFromFile "c:\test.pfx", "pfxpassword", CRYPT_USER_KEYSET ' Set oMail = oMail.Decrypt(oCert) Set oMail = oMail.Decrypt(Nothing) End If If oMail.IsSigned Then ' This email is digital signed. Dim oCert As EAGetMailObjLib.Certificate Set oCert = oMail.VerifySignature MsgBox "This email contains a valid digital signature." ' You can add the certificate to your certificate storage like this ' oCert.AddToStore CERT_SYSTEM_STORE_CURRENT_USER, "addressbook" ' Then you can use send the encrypted email back to this sender. End If ' Parse email sender MsgBox "From: " & oMail.From.Address Dim arAddr Dim i As Integer Dim addr As EAGetMailObjLib.MailAddress ' Parse email to recipients arAddr = oMail.To For i = LBound(arAddr) To UBound(arAddr) Set addr = arAddr(i) MsgBox "To: " & addr.Address Next ' Parse email cc arAddr = oMail.Cc For i = LBound(arAddr) To UBound(arAddr) Set addr = arAddr(i) MsgBox "Cc: " & addr.Address Next ' Parse email subject MsgBox "Subject: " & oMail.Subject ' Parse email text body MsgBox "Text body: " & oMail.TextBody ' Parse email HTML body MsgBox "Html body: " & oMail.HtmlBody Dim atts Dim att As EAGetMailObjLib.Attachment ' Parse attachments atts = oMail.Attachments For i = LBound(atts) To UBound(atts) Set att = atts(i) MsgBox "Attachment: " & att.name Next Exit Sub ErrorHandle: MsgBox Err.Description End Sub Private Sub Command1_Click() ParseEmail "c:\my folder\test.eml" Exit Sub ErrorHandle: MsgBox Err.Description End Sub
Seperate builds of run-time dll for 32 and x64 platform
|Installation Path\EAGetMailObj.dll||32 bit|
|Installation Path\x64\EAGetMailObj.dll||64 bit|
For VB6, C++, Delphi or other standard exe application, you can distribute EAGetMailObj.dll with your application to target machine without COM-registration and installer. To learn more detail, please have a look at Registration-free COM with Manifest File.
For ASP, VBScript, VBA, MS SQL Stored Procedure, you need to install EAGetMail on target machine by EAGetMail installer, both 32bit/x64 DLL are installed and registered.
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