The following vb example codes demonstrate how to sign email to S/MIME format with digital signature.
Email Digital Signature
Digital signature prevents email content is faked or changed in transport level. Encrypting email protects email content from exposure to inappropriate recipients. Both digital signature and email encrypting depend on digital certificate.
If you have an email digital signature certificate installed on your machine, you can find it in “Control Panel” -> “Internet Options” -> “Content” -> “Certificates” -> “Personal”.
Then you can use your email certificate to sign the email by the following code. If you don’t have a certificate for your email address, you MUST get a digital certificate for personal email protection from third-party certificate authorities such as www.verisign.com.
If you need a free certificate for your email address, you can go to http://www.comodo.com/home/email-security/free-email-certificate.php to apply for one year free email certificate.
EASendMail is a SMTP component which supports all operations of SMTP/ESMTP protocols (RFC 821, RFC 822, RFC 2554). Before you can use the following example codes, you should download the EASendMail Installer and install it on your machine at first.
To use EASendMail SMTP ActiveX Object in your project, the first step is “Add reference
of EASendMail to your project”. Please select menu ->
EASendMailObj ActiveX Object, click
OK, the reference will be added
to current project, and you can start to use it to send email in your project.
The following example codes demonstrate signing email with digital signature - S/MIME.
In order to run it correctly, please change
recipient value to yours.
To get full sample projects, please download and install EASendMail on your machine.
Const CRYPT_MACHINE_KEYSET = 32 Const CRYPT_USER_KEYSET = 4096 Const CERT_SYSTEM_STORE_CURRENT_USER = 65536 Const CERT_SYSTEM_STORE_LOCAL_MACHINE = 131072 Const ConnectNormal = 0 Const ConnectSSLAuto = 1 Const ConnectSTARTTLS = 2 Const ConnectDirectSSL = 3 Const ConnectTryTLS = 4 Private Sub btnSendMail_Click() Dim oSmtp As New EASendMailObjLib.Mail oSmtp.LicenseCode = "TryIt" ' Set your sender email address oSmtp.FromAddr = "firstname.lastname@example.org" ' Add recipient email address oSmtp.AddRecipientEx "email@example.com", 0 ' Set email subject oSmtp.Subject = "test email from VB 6.0 with digital signature" ' Set email body oSmtp.BodyText = "this is a test email sent from VB 6.0 with digital signature" ' Add digital signature If Not oSmtp.SignerCert.FindSubject("firstname.lastname@example.org", _ CERT_SYSTEM_STORE_CURRENT_USER, "my") Then MsgBox oSmtp.SignerCert.GetLastError() Exit Sub End If If Not oSmtp.SignerCert.HasPrivateKey Then MsgBox "Signer certificate has not private key, " & _ " this certificate can not be used to sign email!" Exit Sub End If ' Your SMTP server address oSmtp.ServerAddr = "smtp.emailarchitect.net" ' User and password for ESMTP authentication, if your server doesn't require ' User authentication, please remove the following codes. oSmtp.UserName = "email@example.com" oSmtp.Password = "testpassword" ' ConnectTryTLS means if server supports SSL/TLS connection, SSL/TLS is used automatically oSmtp.ConnectType = ConnectTryTLS ' If your server uses 587 port ' oSmtp.ServerPort = 587 ' If your server uses 25/587/465 port with SSL/TLS ' oSmtp.ConnectType = ConnectSSLAuto ' oSmtp.ServerPort = 25 ' 25 or 587 or 465 MsgBox "start to send email ..." If oSmtp.SendMail() = 0 Then MsgBox "email was sent successfully!" Else MsgBox "failed to send email with the following error:" & oSmtp.GetLastErrDescription() End If End Sub
You can use SignatureHashAlgorithm property to set MD5, SHA1, SHA256, SHA384 or SHA512 signature algorithm. SHA256 is recommended.
TLS is the successor of SSL, more and more SMTP servers require
TLS 1.2 encryption now.
If your operating system is
Windows XP/Vista/Windows 7/Windows 2003/2008/2008 R2/2012/2012 R2, you need to
enable TLS 1.2 protocol in your operating system like this:
Seperate builds of run-time dll for 32 and x64 platform
|Installation Path\Lib\native\x86\EASendMailObj.dll||32 bit|
|Installation Path\Lib\native\x64\EASendMailObj.dll||64 bit|
For VB6, C++, Delphi or other standard exe application, you can distribute EASendMailObj.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 EASendMail on target machine by EASendMail installer, both 32bit/x64 DLL are installed and registered.