In this article I will explain with an example, how to send email asynchronously using MailKit library in ASP.Net Core MVC.
Note: For beginners in ASP.Net Core 8, please refer my article ASP.Net Core 8: Hello World Tutorial with Sample Program example.
 
The email will be sent asynchronously using async modifier and await operator.
Note: For more details on async and await in ASP.Net, please refer my article Async and Await example in ASP.Net.
 
 

Installing MailKit package

You will need to install the MailKit package, for more details on installation, please refer my article Install MailKit from Nuget in Visual Studio.
 
 

Mail Server Settings in AppSettings.json file

The Mail Server settings are saved in the SMTP section as shown below.
{
  "Smtp": {
    "Server": "smtp.gmail.com",
    "Port": 587
  }
}
 
 

MimeKit MimeMessage and MailKit SmtpClient class

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 SmtpClient 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.
 
 

Model

The Model class consists of the following properties.
public class EmailModel
{
    public string To { get; set; }
    public string Subject { get; set; }
    public string Body { get; set; }
    public string Email { get; set; }
    public string Password { get; set; }
}
 
 

Namespaces

You will need to import the following namespaces.
using MimeKit;
using MailKit.Net.Smtp;
 
 

Controller

The Controller consists of following Action methods.

Action method for handling GET operation

Inside this Action method, simply the View is returned.
 

Action method for handling POST operation

This Action method handles the call made from the POST function from the View which accepts EmailModel class object as a parameter.
Note: For more details on how to use Model class object for capturing Form field values, please refer my article ASP.Net Core MVC: Form Submit (Post) example.
 
Inside this Action method, the posted values from their respective fields are captured through the EmailModel class object and are passed as parameter to SendEmailAsync method.
The SendEmailAsync method is asynchronous method created using async modifier.
A new Thread object is defined and within which the SendEmailAsync method is called using delegate function.
 

SendEmailAsync

Inside the SendEmailAsync method all these parameters are set into the respective properties of the object of the MimeMessage class.
 

Setting Body of Email

For Body, 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.
 

Sending Email

Then, an object of the SmtpClient class is created and the values of Host and Port are fetched from the SMTP section of the AppSettings.json file and are passed as parameter to the ConnectAsync method.
Finally, the methods of the Mail Server such as ConnectAsync, AuthenticateAsync, SendAsync and DisconnectAsync are executed using await operator and a success message is set to a ViewBag object.
public class HomeController : Controller
{
    public IConfiguration Configuration { get; set; }
 
    public HomeController(IConfiguration _configuration)
    {
        this.Configuration = _configuration;
    }
 
    public IActionResult Index()
    {
        return View();
    }
 
    [HttpPost]
    public IActionResult Index(EmailModel model)
    {
        Thread email = new Thread(delegate ()
        {
            this.SendEmailAsync(model.To, model.Email, model.Password, model.Subject, model.Body);
        });
        ViewBag.Message = "Email Sent.";
        return View();
    }
 
    private async void SendEmailAsync(string to, string from, string password, string subject, string body)
    {
        string host = this.Configuration.GetValue<string>("Smtp:Server");
        int port = this.Configuration.GetValue<int>("Smtp:Port");
 
        using (MimeMessage mm = new MimeMessage())
        {
            mm.From.Add(new MailboxAddress("Sender", from));
            mm.To.Add(new MailboxAddress("Recipient", to));
            mm.Subject = subject;
            BodyBuilder builder = new BodyBuilder();
            builder.TextBody = body;
            mm.Body = builder.ToMessageBody();
            using (SmtpClient smtp = new SmtpClient())
            {
                await smtp.ConnectAsync(host, port);
                await smtp.AuthenticateAsync(from, password);
                await smtp.SendAsync(mm);
                await smtp.DisconnectAsync(true);
            }
        }
    }
}
 
 

View

HTML Markup

Inside the View, the EmailModel class is declared as model for the View and ASP.Net TagHelpers in inherited.
The View consists of an HTML Form which has been created using the following TagHelpers attributes.
asp-action – Name of the Action. In this case the name is Index.
asp-controller – Name of the Controller. In this case the name is Home.
method – It specifies the Form Method i.e. GET or POST. In this case it will be set to POST.
The Form consists of HTML INPUT TextBoxes, TextArea element and a Submit Button.
 

Submitting the Form

When the Send Button is clicked, the Form gets submitted and the Model object is sent to the Controller.
Finally, the ViewBag object is checked for NULL and if it is not NULL then the value of the object is displayed using JavaScript Alert Message Box.
@addTagHelper*, Microsoft.AspNetCore.Mvc.TagHelpers
@model SendEmail_Mailkit_Async_Core_MVC.Models.EmailModel
@{
     Layout = null;
}
 
<!DOCTYPE html>
 
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>    
</head>
<body>
    <form method="post" asp-controller="Home" asp-action="Index">
        <table>
            <tr>
                <td style="width: 80px">To:</td>
                <td><input type="text" asp-for="To" /></td>
            </tr>
            <tr><td>&nbsp;</td></tr>
            <tr>
                <td>Subject:</td>
                <td><input type="text" asp-for="Subject" /></td>
            </tr>
            <tr><td>&nbsp;</td></tr>
            <tr>
                <td valign="top">Body:</td>
                <td><textarea cols="20" rows="3" asp-for="Body"></textarea></td>
            </tr>
            <tr><td>&nbsp;</td></tr>
            <tr>
                <td>Gmail Email:</td>
                <td><input type="text" asp-for="Email" /></td>
            </tr>
            <tr><td>&nbsp;</td></tr>
            <tr>
                <td>Gmail Password:</td>
                <td><input type="password" asp-for="Password" /></td>
            </tr>
            <tr><td>&nbsp;</td></tr>
            <tr>
                <td></td>
                <td><input type="submit" value="Send" /></td>
            </tr>
        </table>
    </form>
    @if (ViewBag.Message != null)
    {
        <script type="text/javascript">
            window.onload = function () {
                alert("@ViewBag.Message");
            };
        </script>
    }
</body>
</html>
 
 

Possible Errors

The possible errors (exceptions) occurring while sending email with MailKit in .Net are covered in the following article.
Error (Exceptions) while sending email with MailKit in .Net
 
 

Screenshots

Email Form

ASP.Net Core: Send email Asynchronously using MailKit
 

Received Email

ASP.Net Core: Send email Asynchronously using MailKit
 
 

Downloads

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