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ASP.NET Core 3.1 - Send Emails via SMTP with MailKit

Tutorial built with ASP.NET Core 3.1

This is a quick example of how to send an email in ASP.NET Core 3.1 using the MailKit email client library.

For more info on MailKit see https://github.com/jstedfast/MailKit.


Installing MailKit via NuGet

.NET Core CLI: dotnet add package MailKit

Visual Studio Package Manager Console: Install-Package MailKit


Sending an HTML email in ASP.NET Core

This code sends a simple HTML email using the Ethereal free SMTP testing service, you can create a free test account in one click at https://ethereal.email/ and copy the username and password from below the title SMTP configuration. See instructions below for using different SMTP providers such as Gmail and Hotmail.

// create email message
var email = new MimeMessage();
email.Sender = MailboxAddress.Parse("[email protected]");
email.To.Add(MailboxAddress.Parse("[email protected]"));
email.Subject = "Test Email Subject";
email.Body = new TextPart(TextFormat.Html) { Text = "<h1>Example HTML Message Body</h1>" };

// send email
using var smtp = new SmtpClient();
smtp.Connect("smtp.ethereal.email", 587, SecureSocketOptions.StartTls);
smtp.Authenticate("[USERNAME]", "[PASSWORD]");
smtp.Send(email);
smtp.Disconnect(true);


Sending a plain text email in ASP.NET Core

This code sends the same email as above with a plain text body.

// create email message
var email = new MimeMessage();
email.Sender = MailboxAddress.Parse("[email protected]");
email.To.Add(MailboxAddress.Parse("[email protected]"));
email.Subject = "Test Email Subject";
email.Body = new TextPart(TextFormat.Plain) { Text = "Example Plain Text Message Body" };

// send email
using var smtp = new SmtpClient();
smtp.Connect("smtp.ethereal.email", 587, SecureSocketOptions.StartTls);
smtp.Authenticate("[USERNAME]", "[PASSWORD]");
smtp.Send(email);
smtp.Disconnect(true);


Changing SMTP Provider (e.g. Gmail, Hotmail, Office365)

To change the above code to use a different email provider simply update the host parameter (the first parameter) passed to the smtp.Connect() method, for example:

// gmail
smtp.Connect("smtp.gmail.com", 587, SecureSocketOptions.StartTls);

// hotmail
smtp.Connect("smtp.live.com", 587, SecureSocketOptions.StartTls);

// office 365
smtp.Connect("smtp.office365.com", 587, SecureSocketOptions.StartTls);


Wrapping it up in an Email Service

To encapsulate the email sending functionality and make it easy to send email from anywhere in your ASP.NET Core application you can create an EmailService class and IEmailService interface like below.

For examples of how this email service is used in a real project see ASP.NET Core 3.1 - Boilerplate API with Email Sign Up, Verification, Authentication & Forgot Password.

using MailKit.Net.Smtp;
using MailKit.Security;
using Microsoft.Extensions.Options;
using MimeKit;
using MimeKit.Text;
using WebApi.Helpers;

namespace WebApi.Services
{
    public interface IEmailService
    {
        void Send(string from, string to, string subject, string html);
    }

    public class EmailService : IEmailService
    {
        private readonly AppSettings _appSettings;

        public EmailService(IOptions<AppSettings> appSettings)
        {
            _appSettings = appSettings.Value;
        }

        public void Send(string from, string to, string subject, string html)
        {
            // create message
            var email = new MimeMessage();
            email.Sender = MailboxAddress.Parse(from);
            email.To.Add(MailboxAddress.Parse(to));
            email.Subject = subject;
            email.Body = new TextPart(TextFormat.Html) { Text = html };

            // send email
            using var smtp = new SmtpClient();
            smtp.Connect(_appSettings.SmtpHost, _appSettings.SmtpPort, SecureSocketOptions.StartTls);
            smtp.Authenticate(_appSettings.SmtpUser, _appSettings.SmtpPass);
            smtp.Send(email);
            smtp.Disconnect(true);
        }
    }
}

 

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