Making Postal send mails with Postmark

In my previous post I praised Postal for being such a simple and easy library to use for templating and sending emails from your .net app. I also briefly mentioned how it just uses the standard SMTP settings from your Web.config or App.config file for sending out the mails.

This is fine in most scenarios, but on one of our last projects we were using Postmark and gave preference to using the HTTP API instead of relying on the SMTP protocol. The main advantage of this is that HTTP tends to be far less chatty than SMTP and you can increase the throughput of your mails.

Step 1: Install Postmark .net library

From the Package Manager Console inside Visual Studio do:

Install-Package Postmark

This installs the official Postmark .net library from NuGet.

Step 2: Implement an IEmailService

An IEmailService is Postal's way to allow you to alter the behaviour of sending the email. The default implementation uses the System.Net.Mail namespace to compose a MailMessage instance and send it using the configuration that sits in your .config file.

This is what we want to change in order to start using the Postmark API, we can send emails using the following code snippet.

    MailMessage message = ...;

    var client = new PostmarkClient("<your api token goes here>");
    client.SendMessageAsync(message);

This is absolutely perfect, because the default EmailService implementation contains a method to create a MailMessage based on an Email object, so we can simply use that and pass the MailMessage to the PostmarkClient. The result is the following service:

    public class PostmarkEmailService : IEmailService
    {
        // the default implementation used to generated
        // the MailMessage objects
        private Postal.EmailService _inner;
        private PostmarkClient _client;

        public PostmarkEmailService(string token)
        {
            _inner = new EmailService();
            _client = new PostmarkClient(token);
        }

        public void Send(Email email)
        {
            var msg = CreateMailMessage(email);
            _client.SendMessageAsync(msg)
                   .Wait();
        }

        public Task SendAsync(Email email)
        {
            var msg = CreateMailMessage(email);
            return _client.SendMessageAsync(msg);
        }

        public MailMessage CreateMailMessage(Email email)
        {
            return _inner.CreateMailMessage(email);
        }
    }

Step 3: Set an instance of our service as the default one

Now that we have a service that can send Emails using the Postmark API, the only thing that remains to be done is to configure Postal the use it as IEmailService used for sending out the mails during the startup of our app.

    Email.CreateEmailService = () => new PostmarkEmailService("<your token goes here>");

Conclusion

That's it! From now on all Send calls on an Email object will use Postmark to send out the emails. Changing Postal's default send implementation is super easy, thanks to the nice NuGet package that Postmark provides and to the extensibility of Postal.