1. create a send grid account

2. remember the username/password of the send grid account

3. install sendgrid nuget pkg

4. get key

manage ->it will redirect you to manage portal

create a new api key:

4. sample code of console application

using System;using System.Net.Mail;using SendGrid;namespace SendGridAzureSample{    class Program    {        static void Main(string[] args)        {            SendGridMessage myMessage = new SendGridMessage();            myMessage.AddTo("send_to");            myMessage.From = new MailAddress("from_email", "Display name");            myMessage.Subject = "Testing the SendGrid Library";            myMessage.Text = "Hello World!";            //myMessage.AddAttachment(@"attachment_path");            var key = "your_key";            // create a Web transport, using API Key            var transportWeb = new Web(key);            transportWeb.DeliverAsync(myMessage);            Console.ReadKey();        }    }}

reference link : https://azure.microsoft.com/en-us/documentation/articles/sendgrid-dotnet-how-to-send-email/