NServiceBus endpoint that handles email

gistfile1.cs

using System;
using System.Configuration;
using System.Net;
using System.Text;
using NServiceBus;
using Newtonsoft.Json;
using RestSharp;

    public class SendEmailHandler : IHandleMessages<SendEmail>
    {
        private readonly IBus m_bus;

        public SendEmailHandler(IBus bus)
        {
            m_bus = bus;
        }

        public void Handle(SendEmail message)
        {
            var request = new RestRequest();
            request.AddParameter("domain", ConfigurationManager.AppSettings["Mailgun.Domain"], ParameterType.UrlSegment);
            request.Resource = "{domain}/messages";
            
            request.AddParameter("from", message.From.ToMailgunParameter());
            message.To.ForEach(to => request.AddParameter("to", to.ToMailgunParameter()));
            (message.Bcc ?? new MailAddress[0]).ForEach(to => request.AddParameter("bcc", to.ToMailgunParameter()));
            request.AddParameter("subject", message.Subject);
            request.AddParameter(message.BodyFormat == EmailFormat.Html ? "html" : "text", message.Body);
            (message.Attachments ?? new Attachment[0]).ForEach(attachment => request.AddFile("attachment", attachment.Contents, attachment.FileName, attachment.MimeType));

            // These allow out of office messages to get back to the sender instead of Mailgun
            request.AddParameter("o:native", "True");
            request.AddParameter("o:native-send", "True");

            request.Method = Method.POST;

            var client = new RestClient {
                BaseUrl = "https://api.mailgun.net/v2",
                Authenticator = new HttpBasicAuthenticator("api", ConfigurationManager.AppSettings["Mailgun.ApiKey"])
            };

            var response = client.Execute(request);

            if (response.StatusCode != HttpStatusCode.OK)
                ThrowException(response);

            m_bus.Reply(new EmailSent());
        }

        private void ThrowException(IRestResponse response)
        {
            var sb = new StringBuilder("Did not receive the expected HTTP OK response from Mailgun.");
            sb.AppendLine("Instead, received this response:");
            sb.AppendLine(JsonConvert.SerializeObject(response, Formatting.Indented));
            throw new Exception(sb.ToString());
        }
        
        
    }
    
    public class SendEmail : IMessage
    {
        public MailAddress[] To { get; set; }

        public MailAddress From { get; set; }

        public MailAddress[] Bcc { get; set; }

        public string Subject { get; set; }

        public string Body { get; set; }

        public EmailFormat BodyFormat { get; set; }

        public Attachment[] Attachments { get; set; }
    }
    
    public class Attachment
    {
        public string FileName { get; set; }
        public byte[] Contents { get; set; }
        public string MimeType { get; set; }
    }
    
    public class MailAddress
    {
        public string Address { get; set; }
        public string DisplayName { get; set; }
    }