In this article I will explain with an example, how to send email using Gmail and
MailKit in ASP.Net WebForms with C# and VB.Net.
Installing MailKit package
Mail Server Settings in Web.Config file
The following Mail Server settings need to be saved in the Web.Config file.
<system.net>
<mailSettings>
<smtp deliveryMethod="Network">
<network
host="smtp.gmail.com"
port="587" />
</smtp>
</mailSettings>
</system.net>
HTML Markup
The HTML Markup consists of following controls:
TextBox – For capturing the values of Recipient Email address, Subject, Body, Gmail account email address, Gmail account password.
FileUpload – For attaching file to the email.
Button – For sending email.
The Button has been assigned with an OnClick event handler.
<table border="0" cellpadding="0" cellspacing="0">
<tr>
<td style="width: 80px">To:</td>
<td><asp:TextBox ID="txtTo" runat="server"></asp:TextBox></td>
</tr>
<tr><td> </td></tr>
<tr>
<td>Subject:</td>
<td><asp:TextBox ID="txtSubject" runat="server"></asp:TextBox></td>
</tr>
<tr><td> </td></tr>
<tr>
<td valign="top">Body:</td>
<td><asp:TextBox ID="txtBody" runat="server" TextMode="MultiLine" Height="150" Width="200"></asp:TextBox></td>
</tr>
<tr>
<td>File Attachment:</td>
<td><asp:FileUpload ID="fuAttachment" runat="server" /></td>
</tr>
<tr><td> </td></tr>
<tr>
<td>Gmail Email:</td>
<td><asp:TextBox ID="txtEmail" runat="server"></asp:TextBox></td>
</tr>
<tr><td> </td></tr>
<tr>
<td>Gmail Password:</td>
<td><asp:TextBox ID="txtPassword" runat="server" TextMode="Password"></asp:TextBox></td>
</tr>
<tr><td> </td></tr>
<tr>
<td></td>
<td><asp:Button ID="btnSend" Text="Send" OnClick="SendEmail" runat="server" /></td>
</tr>
</table>
Namespaces
You will need to import the following namespaces.
C#
using MimeKit;
using MailKit.Net.Smtp;
using MailKit.Security;
using System.IO;
using System.Configuration;
using System.Net.Configuration;
VB.Net
Imports MimeKit
Imports MailKit.Net.Smtp
Imports MailKit.Security
Imports System.IO
Imports System.Configuration
Imports System.Net.Configuration
Sending email with Attachment using MailKit
MimeMessage Class Properties
Following are the required properties of the MimeMessage class.
From – Sender’s email address.
To – Recipient(s) Email Address.
CC – Carbon Copies. (If any)
BCC – Blind Carbon Copies. (If any)
Subject – Subject of the Email.
Body – Body of the Email.
Attachments – Attachments. (If any)
ReplyTo – ReplyTo Email address.
SmtpClient Class Methods
Following are the methods of the SMTP class.
Connect – The connection to the SMTP Server is established using the domain and the port number.
Authenticate – The username and password of the SMTP Server is authenticated.
Send – The MimeMessage object is passed to it and the email is sent.
Disconnect – Disconnects the connection with SMTP Server.
Sending Email
When the SendEmail Button is clicked, the Recipient email address (to), the Sender email address (from), Subject, Body and Attachment details are fetched from their respective fields and are set into the respective properties of the object of the MimeMessage class.
Setting Body of Email
For Body and Attachment, an object of Builder class is created. The Body of the email is Text (Non HTML) hence it is set into the TextBody property of the Builder class object.
Attaching File
The FileUpload is checked for Attachment and if it has File then the posted File is added as Attachment to the Builder object.
Sending Email
Then, an object of the SmtpClient class is created and the values of Host, Port are fetched from the SMTP section of the Web.Config file and are passed as parameter to Connect method along with the SecureSocketOptions set to Auto.
Note: Setting Auto allows
MailKit service to decide which SSL or TLS option to use. Hence, enabling SSL is not required.
Also, the CheckCertificateRevocation is set to FALSE.
Note: This is optional and must be used only when Certificate errors are occurring.
Finally, the methods of the Mail Server such as
Connect,
Authenticate,
Send and
Disconnect are executed and a success message is displayed in
JavaScript Alert
MessageBox using
RegisterStartupScript method.
C#
protected void SendEmail(object sender, EventArgs e)
{
string to = txtTo.Text;
string from = txtEmail.Text;
string password = txtPassword.Text;
string subject = txtSubject.Text;
string body = txtBody.Text;
HttpPostedFile postedFile = fuAttachment.PostedFile;
//Read SMTP section from Web.Config.
SmtpSection smtpSection = (SmtpSection)ConfigurationManager.GetSection("system.net/mailSettings/smtp");
string host = smtpSection.Network.Host;
int port = smtpSection.Network.Port;
using (MimeMessage mm = new MimeMessage())
{
mm.From.Add(new MailboxAddress("Sender", from));
mm.To.Add(new MailboxAddress("Recepient", to));
mm.Subject = subject;
BodyBuilder builder = new BodyBuilder()
{
TextBody = body
};
//Check whether any Attachment is present and attach it.
if (postedFile.ContentLength > 0)
{
string fileName = Path.GetFileName(postedFile.FileName);
builder.Attachments.Add(fileName, postedFile.InputStream);
}
mm.Body = builder.ToMessageBody();
using (SmtpClient smtp = new SmtpClient())
{
//Set to False to avoid Certificate verification.
smtp.CheckCertificateRevocation = false;
smtp.Connect(host, port, SecureSocketOptions.Auto);
smtp.Authenticate(from, password);
smtp.Send(mm);
smtp.Disconnect(true);
}
}
ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('Email sent.');", true);
}
VB.Net
Protected Sub SendEmail(ByVal sender As Object, ByVal e As EventArgs)
Dim [to] As String = txtTo.Text
Dim from As String = txtEmail.Text
Dim password As String = txtPassword.Text
Dim subject As String = txtSubject.Text
Dim body As String = txtBody.Text
Dim postedFile As HttpPostedFile = fuAttachment.PostedFile
'Read SMTP section from Web.Config.
Dim smtpSection As SmtpSection = CType(ConfigurationManager.GetSection("system.net/mailSettings/smtp"), SmtpSection)
Dim host As String = smtpSection.Network.Host
Dim port As Integer = smtpSection.Network.Port
Using mm As MimeMessage = New MimeMessage()
mm.From.Add(New MailboxAddress("Sender", from))
mm.[To].Add(New MailboxAddress("Recepient", [to]))
mm.Subject = subject
Dim builder As BodyBuilder = New BodyBuilder() With {
.TextBody = body
}
'Check whether any Attachment is present and attach it.
If postedFile.ContentLength > 0 Then
Dim fileName AsString = Path.GetFileName(postedFile.FileName)
builder.Attachments.Add(fileName, postedFile.InputStream)
EndIf
mm.Body = builder.ToMessageBody()
Using smtp As SmtpClient = New SmtpClient()
'Set to False to avoid Certificate verification.
smtp.CheckCertificateRevocation = False
smtp.Connect(host, port, SecureSocketOptions.Auto)
smtp.Authenticate(from, password)
smtp.Send(mm)
smtp.Disconnect(True)
End Using
End Using
ClientScript.RegisterStartupScript(Me.GetType(), "alert", "alert('Email sent.');", True)
End Sub
Possible Errors
The possible errors (exceptions) occurring while sending email with
MailKit in .Net are covered in the following article.
Screenshots
Email Form
![Send Email using Gmail and MailKit in ASP.Net]()
Received Email
![Send Email using Gmail and MailKit in ASP.Net]()
Downloads
