Great! You want a step-by-step tutorial on using the email service in Umbraco 8, based on the code inside your latest HighlyDeveloped.Core.zip.
I’ll extract and examine your code, then write a clear guide on best-practice email sending (and settings) for Umbraco 8, including practical usage examples.

Let’s start by extracting and reviewing your code.

Here’s what’s relevant for emailing in your codebase:

• Services/EmailService.cs (the actual email-sending logic)

• Interfaces/IEmailService.cs (the contract/interface)

• RegisterServicesComposer.cs (dependency injection registration for Umbraco’s DI container)

Let’s review these files and then I’ll walk you through using your email service in Umbraco 8, following best practices.

Let’s look at the interface first.

Your interface is simple and clear:

public interface IEmailService
{
    void SendContactNotificationToAdmin(ContactFormViewModel vm);
}

• It requires an implementation to send a contact notification email to admin, given a view model.

Let’s see how the service actually sends the email.

Your EmailService does the following (following best practices for an Umbraco 8 service):

• Uses dependency injection for Umbraco services (UmbracoHelper, IContentService, ILogger).

• Fetches email templates from Umbraco content nodes (dynamic, editable by content editors).

• Reads email addresses (From, To, Test accounts) and a test/debug mode flag from Site Settings.

• Uses mail merge to personalize template content (replaces ##name##, ##email##, etc).

• Logs all sent emails as Umbraco content nodes (audit trail).

• Sends email via SmtpClient with HTML and plain text support.

• Catches and logs errors robustly.

Let’s quickly check the composer to ensure you can inject IEmailService anywhere.

Your RegisterServicesComposer properly registers your service:

public class RegisterServicesComposer : IUserComposer
{
    public void Compose(Composition composition)
    {
        composition.Register<IEmailService, EmailService>(Lifetime.Request);
    }
}

• This means anywhere in Umbraco 8, you can inject IEmailService and use it!

In your Umbraco backoffice, under Settings → Document Types, ensure you have a siteSettings node with:

• emailSettingsFromAddress (Textstring)

• emailSettingsAdminAccounts (Textbox Multiple, comma-separated for multiple emails)

• testMode (True/False)

• emailTestAccounts (Textbox Multiple)

Create a Document Type: emailTemplate with:

• emailTemplateSubjectLine (Textstring)

• emailTemplateHtmlContent (Richtext Editor or Textbox)

• emailTemplateTextContent (Textbox)

Create a node named "New Contact Form Notification" (or any name you want) under a folder like "Emails".

• In your HTML/Text, use merge fields like ##name##, ##email##, ##comment##.

In any SurfaceController, Composer, or Service, inject the interface:

private readonly IEmailService _emailService;
public MyController(IEmailService emailService)
{
_emailService = emailService;
}

In SurfaceControllers, if you use parameterless constructors, you can resolve with Current.Factory.GetInstance<IEmailService>().

When you want to send an email:

using HighlyDeveloped.Core.ViewModel;
public ActionResult SubmitContact(ContactFormViewModel vm)
{
// ... your form validation, captcha, etc ...
_emailService.SendContactNotificationToAdmin(vm);

// Show success to user, etc.
TempData["status"] = "OK";
return RedirectToCurrentUmbracoPage();

}

• The SendContactNotificationToAdmin method handles everything: template, merge, logging, sending.

• Email content is editable in Umbraco—no redeploy needed to change wording or design.

• All sent emails are logged as Umbraco content (you can review/audit later).

• Debug/test mode lets you redirect all emails to a test inbox safely.

• Full error logging using Umbraco’s logging abstraction.

Set your SMTP settings in your web.config (or via appSettings):

<system.net>
  <mailSettings>
    <smtp from="[email protected]">
      <network host="smtp.yourdomain.com" port="587" userName="smtpuser" password="smtppassword" enableSsl="true" />
    </smtp>
  </mailSettings>
</system.net>

Tip: Use a transactional email service (e.g., SendGrid, Mailgun) for reliability, especially in production.

• Make sure you create at least one emailTemplate and set up your site settings node.

• Try submitting a contact form—emails should be logged under your "Emails" folder and delivered.

1. Configure: All addresses and templates are editable in Umbraco.

2. Inject: Use the DI container to inject your service.

3. Send: Call the appropriate method (SendContactNotificationToAdmin).

4. Audit: All emails are saved as Umbraco content for history/auditing.

5. Safe Testing: Flip a switch in site settings to enter test mode.

You now have a professional, maintainable, and testable email infrastructure in your Umbraco 8 project!
If you want an example of customizing a new template or sending a different kind of email (e.g., password reset, welcome message), just ask!