In this article I will explain with an example, how to send Email using HTML Templates in ASP.Net Core Razor Pages.
Note: For more details on how to send email in ASP.Net Core Razor Pages, please refer my article ASP.Net Core Razor Pages: Contact Us Form.
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 Razor Pages: 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 Razor Pages: 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 />
Index PageModel (Code-Behind)
The PageModel consists of the following Handler methods.
Handler method for handling GET operation
This Handler method is left empty as it is not required.
Handler method for handling POST operation
Inside this Handler 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 IndexModel : PageModel
    private IHostingEnvironment Environment { get; set; }
    public IConfiguration Configuration { get; set; }
    public IndexModel(IConfiguration _configuration, IHostingEnvironment environment)
        Configuration = _configuration;
        Environment = environment;
    public void OnGet()
    public void OnPostSendEmail()
        string userName = "John";
        string title = "ASP.Net Core Razor Pages: 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 Razor Pages in ASP.Net Core 2.0 for the first time.";
        string body = this.PopulateBody(userName, title, url, description);
        this.SendHtmlFormattedEmail("", "New article published!", body);   
    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)
        //Read SMTP section from AppSetting.json.
        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;
Razor Page (HTML)
Inside the Razor Page, the ASP.Net TagHelpers is inherited.
The HTML of Razor Page consists of:
Form - For sending Request.
The Submit Button has been set with the POST Handler method using the asp-page-handler attribute.
Note: In the Razor PageModel, the Handler method name is OnPostSendEmail but here it will be specified as SendEmail when calling from the Razor HTML Page.
@addTagHelper*, Microsoft.AspNetCore.Mvc.TagHelpers
@model Send_Email_Template_Core_Razor.Pages.IndexModel
    Layout = null;
<!DOCTYPE html>
    <meta name="viewport" content="width=device-width" />
    <form method="post">
        <input type="submit" value="Send" asp-page-handler="SendEmail" />
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 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 Razor Pages: Send Email using HTML Templates