In this article I will explain with an example, how to send Email using HTML Templates in ASP.Net Core MVC.
Note: For more details on how to send email in ASP.Net Core MVC, please refer my article Send Email in ASP.Net MVC Core.
The very first step is to Right Click the Project in the Solution Explorer and click Add and then New Item and then select HTML Page and name it as EmailTemplate.htm.
ASP.Net Core: Send Email using HTML Templates
Location of the EmailTemplate
The Email Template is placed inside the Template Folder (Directory) in Project Folder.
ASP.Net Core: Send Email using HTML Templates
Building HTML Template for Email Body
The HTML Template of the Email will be built by generating an HTML containing some placeholders which will be replaced with the actual content.
Advantage of creating templates instead of building HTML using String Builder class or String concatenation in code is that one can easily change the HTML of the template without changing the code.
The following HTML Email Template consists of four placeholders:
{UserName} – Name of the recipient.
{Url} – Url of the article.
{Title} – Title of the article.
{Description} – Description of the Article.
These placeholders will be replaced with the actual (real) values when the email is being sent.
<html xmlns="">
    <img style="background:black;" src="" /><br /><br />
    <div style="border-top:3px solid #61028D">&nbsp;</div>
    <span style="font-family:Arial; font-size:10pt">
        Hello <b>{UserName}</b>,<br /><br />
        A new article has been published on ASPSnippets.<br /><br/>
        <a style="color:#61028D" href="{Url}">{Title}</a><br />
        <br /><br />
        Thanks<br />
The Controller consists of the 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, the PopulateBody method is called.
Inside the PopulateBody method, the path of the EmailTemplate file is read using HostingEnvironment interface.
Note: For more details about IHostingEnvironment interface, please refer Using IHostingEnvironment in ASP.Net Core.
Next, the contents of the HTML Email Template file are read into a String variable using the StreamReader class.
Then, the placeholders will be replaced with their respective values and the replaced values are returned.
Next, SendHtmlFormattedEmail method is called.
The SendHtmlFormattedEmail method accepts email address (recepientEmail), Subject and Body parameters.
The Sender email address (from) is fetched from the Smtp section of the AppSettings.json file, the Subject and Body are set from the parameters.
Then, all these values are set into an object of the MailMessage class.
Finally, object of the SmtpClient class is created and the settings of the Mail Server such as Host, Port, Username and Password are fetched from the Smtp section of the AppSettings.json file and are set in respective properties of the SmtpClient class object.
Note: It is necessary to use the sender’s email address credentials while defining the Gmail SMTP Server Credentials as Gmail the sender’s email address must be same as the Gmail Username specified in credentials.
public class HomeController : Controller
    private IHostingEnvironment Environment { get; set; }
    public IConfiguration Configuration { get; set; }
    public HomeController(IConfiguration _configuration, IHostingEnvironment environment)
        Configuration = _configuration;
        Environment = environment;
    public IActionResult Index()
        return View();
    public IActionResult SendEmail()
        string userName = "John";
        string title = "ASP.Net MVC Core Hello World Tutorial with Sample Program example";
        string url = "";
        string description = "Here Mudassar Khan has provided a short Hello World Tutorial using a small Sample Program example on how to use and develop applications in ASP.Net MVC Core 2.1 for the first time.";
        string body = this.PopulateBody(userName, title, url, description);
        this.SendHtmlFormattedEmail("", "New article published!", body);
        return View();
    private string PopulateBody(string userName, string title, string url, string description)
        string body = string.Empty;
        string path = Path.Combine(this.Environment.WebRootPath , "Template\\EmailTemplate.htm");
        using (StreamReader reader = new StreamReader(path))
            body = reader.ReadToEnd();
        body = body.Replace("{UserName}", userName);
        body = body.Replace("{Title}", title);
        body = body.Replace("{Url}", url);
        body = body.Replace("{Description}", description);
        return body;
    private void SendHtmlFormattedEmail(string recepientEmail, string subject, string body)
        string host = this.Configuration.GetValue<string>("Smtp:Server");
        int port = this.Configuration.GetValue<int>("Smtp:Port");
        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, recepientEmail))
            mm.Subject = subject;
            mm.Body = body;
            mm.IsBodyHtml = true;
            using (SmtpClient smtp = new SmtpClient())
                smtp.Host = host;
                smtp.EnableSsl = true;
                NetworkCredential networkCred = new NetworkCredential(userName, password);
                smtp.UseDefaultCredentials = true;
                smtp.Credentials = networkCred;
                smtp.Port = port;
The View consists of an HTML Form with following ASP.Net Tag Helpers 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 a Submit Button, which when clicked the form is submitted.
@addTagHelper*, Microsoft.AspNetCore.Mvc.TagHelpers
    Layout = null;
<!DOCTYPE html>
    <meta name="viewport" content="width=device-width" />
    <form method="post" asp-controller="Home" asp-action="SendEmail">
        <input type="submit" value="Send" />
Mail Server Settings in AppSettings.json file
The mail server settings are saved in the Smtp section as shown below.
 "ConnectionStrings": {
 "Smtp": {
    "Port": 587,
Possible Errors
The following error occurs when you try to send email using Gmail credentials in your ASP.Net 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
ASP.Net Core: Send Email using HTML Templates