ay.Aspire.For.MailKit

This project implements Create custom .NET Aspire hosting integrations and hooks up Aspire with MailKit as described.

Integration

To integrate MailKit with Aspire use the following example. The integration will spin up a MailDev container where you will receive your emails.

The connection string is stored under 'ConnectionString:SmtpServer', either by using MailKit and environment variables or by configuring it in the appsettings.json. During the use of Aspire, the connection string will be provided in the environment variable ConnectionString__SmtpServer by Aspire.

Hosting

In your Aspire project integrate MailKit like so:

var builder = DistributedApplication.CreateBuilder(args);

var maildev = builder.AddMailDev("SmtpServer");

var webApi = builder.AddProject<[REPLACE WITH YOUR PROJECT]>("webApi")
    .WithReference(maildev);

builder.Build().Run();

Client

In your client hosted by Aspire, integrate like so:

builder.AddMailKitClient("SmtpServer");

Then inject the MailKitClientFactory like so into your controller or service. The factory will create an SmtpClient instance that already authenticated to the server if the server supports authentication and if the username is not empty. Make sure that you dispose the SmtpClient instance properly by using using or by calling .Dispose() on the instance.

app.MapPost("/subscribe",
    async (MailKitClientFactory factory, string email) =>
    {
        using var message = new MailMessage("[email protected]", email)
        {
            Subject = "Welcome to our newsletter!",
            Body = "Thank you for subscribing to our newsletter!"
        };

        using var client = await factory.GetSmtpClientAsync();
        
        await client.SendAsync(MimeMessage.CreateFromMailMessage(message));
        await client.DisconnectAsync(true);
    });

And create your ISmtpClient to send an email.

To configure the connection to the SMTP server use

{
  ...
  "ConnectionStrings": {
    "SmtpServer": "Endpoint=smtp://smtp.example.com:587;Username=foo;Password=bar;DisableHealthChecks=true;DisableTracing=true;DisableMetrics=true",
  },
  ...
}

In case you only have an endpoint without authentication, you can shorten it to

{
  ...
  "ConnectionStrings": {
    "SmtpServer": "smtp://smtp.example.com:587",
  },
  ...
}

Alternatively use MailKit settings, but note that a ConnectionString will override the MailKit settings.

{
  ...
  "MailKit": {
    "Client": {
      "Endpoint": "smtp://smtp.example.com:587",
      "Username": "foo",
      "Password": "bar",
      "DisableHealthChecks": true,
      "DisableTracing": true,
      "DisableMetrics": true
    }
  }
  ...
}