The following vb.net example codes demonstrate how to add DomainKeys and DKIM signature to email and send it using SMTP server.
DKIM and DomainKeys
DomainKeys is a technology proposal that can bring black and white back to this decision process by giving email providers a mechanism for verifying both the domain of each email sender and the integrity of the messages sent. To learn more detail about DomainKeys, please refer to http://antispam.yahoo.com/domainkeys
DKIM is a similar technology as Domainkeys. To learn more detail about DKIM, please refer to RFC4871.
Before you can add DomainKeys and DKIM signature to email, you need to generate the certificate and X-DK-File like this:
Download Certificate for your DomainKeys/DKIM key pair
Please click here to go to this online tool at first. Then input your email sender domain in it and click “Download Certificate” and save the downloaded *.pfx file to your local disk. This file contains your DomainKeys and DKIM key pair.
To sign the DomainKeys with EASendMail, we also need to create a text file with notepad and save it.
For example: We create a emailarchitectdomainkeys.txt and contains the following content:
dk_d: emailarchitect.net dk_s: s1024 PFXPath: c:\my cert\emailarchitect.pfx PFXPassword: mypassword DKIM: yes DomainKey: yes // dk_d is the email sender domain, // dk_s is the domain public key selector. // PFXPath is the PFX file full path. // PFXPassword is the PFX file password.
We also need to deploy the certificate Public Key to your domain DNS server. You can export the public key by the online tool:
Deploy Public Key
Once you get the public key, you should set a TXT record in your domain DNS server. For example: your selector is s1024, your domain is emailarchitect.net, and then you should create a TXT record for s1024._domainkey.emailarchitect.net and set the following content in the record.
s1024._domainkey.emailarchitect.net text = "t=y; k=rsa; p=MIGfMA0GCSqGS...hSinuQIDAQAB"
To learn more detail about Public Key deployment, please refer to http://antispam.yahoo.com/domainkeys
Before you can use the following codes, please download EASendMail SMTP Component and install it on your machine at first. Full sample proejcts are included in this installer.
Install from NuGet
You can also install the run-time assembly by NuGet. Run the following command in the NuGet Package Manager Console:
If you install it by NuGet, no sample projects are installed, only .NET assembly is installed.
To use EASendMail SMTP Component in your project, the first step is
of EASendMail to your project. Please create or open your project with Visual Studio,
then go to
Add Reference ->
Browse..., and select
Installation Path\Lib\net[version]\EASendMail.dll from your disk, click
OK, the reference of EASendMail
will be added to your project, and you can start to use it to send email
in your project.
Because EASendMail has separate builds for .Net Framework, please refer to the following table and choose the correct dll.
Separate builds of run-time assembly for .NET Framework 1.1, 2.0, 3.5, 4.0, 4.5, 4.6.1, .NET Core 2.1 and .NET Compact Framework 2.0, 3.5.
|File||.NET Framework Version|
Built with .NET Framework 1.1
It requires .NET Framework 1.1, 2.0, 3.5 or later version.
Built with .NET Framework 2.0
It requires .NET Framework 2.0, 3.5 or later version.
Built with .NET Framework 3.5
It requires .NET Framework 3.5 or later version.
Built with .NET Framework 4.0
It requires .NET Framework 4.0 or later version.
Built with .NET Framework 4.5
It requires .NET Framework 4.5 or later version.
Built with .NET Framework 4.6.1
It requires .NET Framework 4.6.1 or later version.
Built with .NET Core 2.1
It requires .NET Core 2.1 or later version.
Built with .NET Compact Framework 2.0
It requires .NET Compact Framework 2.0, 3.5 or later version.
Built with .NET Compact Framework 3.5
It requires .NET Compact Framework 3.5 or later version.
The following example codes demonstrate sending email with DomainKeys and DKIM signature.
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.
' Add EASendMail namespace Imports EASendMail Module Module1 Sub Main() Try Dim oMail As New SmtpMail("TryIt") ' Set sender email address, please change it to yours oMail.From = "firstname.lastname@example.org" ' Set recipient email address, please change it to yours oMail.To = "email@example.com" ' Set email subject oMail.Subject = "test email from VB.NET with DKIM" ' Set email body oMail.TextBody = "this is a test email sent from VB.NET project, do not reply" ' Add DomainKeys and DKIM configuration file ' Then this email will be signed automatically oMail.Headers.ReplaceHeader("X-DK-File", "c:\emailarchitectdomainkeys.txt") ' Your SMTP server address Dim oServer As New SmtpServer("smtp.emailarchitect.net") ' User and password for ESMTP authentication, if your server doesn't require ' User authentication, please remove the following codes. oServer.User = "firstname.lastname@example.org" oServer.Password = "testpassword" ' Most mordern SMTP servers require SSL/TLS connection now. ' ConnectTryTLS means if server supports SSL/TLS, SSL/TLS will be used automatically. oServer.ConnectType = SmtpConnectType.ConnectTryTLS ' If your SMTP server uses 587 port ' oServer.Port = 587 ' If your SMTP server requires SSL/TLS connection on 25/587/465 port ' oServer.Port = 25 ' 25 or 587 or 465 ' oServer.ConnectType = SmtpConnectType.ConnectSSLAuto Console.WriteLine("start to send email ...") Dim oSmtp As New SmtpClient() oSmtp.SendMail(oServer, oMail) Console.WriteLine("email was sent successfully!") Catch ep As Exception Console.WriteLine("failed to send email with the following error:") Console.WriteLine(ep.Message) End Try End Sub End Module
If your SMTP server has implemented DKIM, you don’t have to sign DKIM in your codes, your email will be signed by your server automatically.
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: