In this article I will explain with an example, how to read Email Settings from AppSettings.json in ASP Net Core (.Net Core 8) MVC.
Note: For beginners in ASP.Net Core (.Net Core 8) MVC, please refer my article ASP.Net Core 8: Hello World Tutorial with Sample Program example.
 
 

Mail Server Settings in AppSettings.json file

The following Mail Server settings need to be saved in the AppSettings.json file.
{
  "Smtp": {
    "Server": "smtp.gmail.com",
    "Port": 587,
    "EnableSsl": true,
    "DefaultCredentials": false,
    "FromAddress": "sender@gmail.com",
    "UserName": "sender@gmail.com",
    "Password": "GMAILor2STEP-PASSWORD"
  }
}
 
 

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; }
}
 
 

Namespaces

You will need to import the following namespaces.
using System.Net;
using System.Net.Mail;
 
 

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

Inside this Action method handles the call made from the POST function from the View.
Note: This example uses Model class object for capturing Form field values, for more details please refer my article ASP.Net MVC: Form Submit (Post) example.
 
When the Form is submitted, the posted values are captured through the EmailModel class object. All the fetched values are set into an object of the MailMessage class.
Then an object of the SmtpClient class is created, where the settings of the Mail Server are read from the AppSettings.json file using IConfiguration interface.
Note: For more information about the IConfiguration interface, please refer my article Using IConfiguration in ASP.Net Core.
 
Finally, the email is being sent using Send method of SmtpClient class object and a success message is display in View.
public class HomeController : Controller
{
    private IConfiguration Configuration;
 
    public HomeController(IConfiguration _configuration)
    {
        this.Configuration = _configuration;
    }
 
    //Get: Home
    public IActionResult Index()
    {
        return View();
    }
 
    [HttpPost]
    public IActionResult Index(EmailModel model)
    {
        //Read SMTP settings from AppSettings.json.
        string host = this.Configuration.GetValue<string>("Smtp:Server");
        int port = this.Configuration.GetValue<int>("Smtp:Port");
        bool enableSsl = this.Configuration.GetValue<bool>("Smtp:EnableSsl");
        bool defaultCredentials = this.Configuration.GetValue<bool>("Smtp:DefaultCredentials");
        string fromAddress = this.Configuration.GetValue<string>("Smtp:FromAddress");
        string userName = this.Configuration.GetValue<string>("Smtp:UserName");
        string password = this.Configuration.GetValue<string>("Smtp:Password");
 
        using (MailMessage mm = new MailMessage(fromAddress, model.To))
        {
            mm.Subject = model.Subject;
            mm.Body = model.Body;
            mm.IsBodyHtml = false;
            using (SmtpClient smtp = new SmtpClient())
            {
                smtp.Host = host;
                smtp.Port = port;
                smtp.EnableSsl = enableSsl;
                smtp.UseDefaultCredentials = defaultCredentials;
                smtp.Credentials = new NetworkCredential(userName, password);
                smtp.Send(mm);
            }
        }
 
        return View();
    }
}
 
 

View

HTML Markup

The View consists of an HTML Form with following ASP.Net Tag Helpers attributes and a Submit Button.
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 TextBox, TextArea and a Submit Button.
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 AppSettings_Email_MVC_Core.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 border="0" cellpadding="0" cellspacing="0">
            <tr>
                <td style="width: 80px">To:</td>
                <td><input type="text" name="To" /></td>
            </tr>
            <tr>
                <td>Subject:</td>
                <td><input type="text" name="Subject" /></td>
            </tr>
            <tr>
                <td valign="top">Body:</td>
                <td><textarea cols="20" rows="10" name="Body"></textarea></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>
 
 

Errors while sending Email using Gmail

The following error occurs when you try to send email using Gmail credentials in your ASP.Net MVC application.
The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required. Learn more at
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.Net.Mail.SmtpException: The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required. Learn more at
 

Solution

GMAIL Error: The SMTP server requires a secure connection or the client was not authenticated
 
 

Screenshots

Email Form

Read Email Settings from AppSettings.json in ASP.Net Core
 

Received Email

Read Email Settings from AppSettings.json in ASP.Net Core
 
 

Downloads

AppSettings_Email_MVC_Core.zip