Customizing Email Templates

Where templates live

All email templates are in src/Acme.Infrastructure/Email/Templates/. Each template is a C# class that extends EmailTemplateBase.

src/Acme.Infrastructure/Email/Templates/
├── EmailTemplateBase.cs          ← base class with HTML scaffolding
├── WelcomeTemplate.cs
├── EmailVerificationTemplate.cs
├── PasswordResetTemplate.cs
├── MagicLinkTemplate.cs
├── PasswordChangedTemplate.cs
├── TenantInvitationTemplate.cs
├── TrialExpiry7DayTemplate.cs
├── TrialExpiry1DayTemplate.cs
├── PaymentFailedTemplate.cs
├── PaymentRecoveredTemplate.cs
├── CancellationScheduledTemplate.cs
└── CancellationConfirmedTemplate.cs

How templates work

EmailTemplateBase provides:

The outer HTML envelope (DOCTYPE, <head>, brand color, inline styles)
Header with the application name
Footer with unsubscribe language
Abstract RenderContent() method that each template implements

Each template class fills in RenderContent() with its specific body HTML:

// EmailVerificationTemplate.cs
public class EmailVerificationTemplate : EmailTemplateBase
{
    private readonly string _userName;
    private readonly string _verificationUrl;

    public EmailVerificationTemplate(string userName, string verificationUrl)
    {
        _userName = userName;
        _verificationUrl = verificationUrl;
    }

    protected override string RenderContent()
    {
        return $"""
            <h2 style="color: #1A56DB; font-size: 20px; margin: 0 0 16px;">
                Verify your email address
            </h2>
            <p style="color: #374151; margin: 0 0 24px;">
                Hi {_userName}, click the button below to verify your email address.
                This link expires in 24 hours.
            </p>
            <a href="{_verificationUrl}"
               style="background: #1A56DB; color: white; padding: 12px 24px;
                      text-decoration: none; border-radius: 6px; display: inline-block;">
                Verify Email
            </a>
            """;
    }
}

Changing the brand color

The primary color is set in one place in EmailTemplateBase:

// EmailTemplateBase.cs
private const string PrimaryColor = "#1A56DB";

Change this value and it propagates to every template header, button, and accent element.

Changing email copy

Find the relevant template class, edit the string in RenderContent(). The C# raw string literal ("""...""") makes multi-line HTML easy to write and read.

Adding a logo

Replace the text-based header in EmailTemplateBase.RenderHeader() with an <img> tag:

// Before:
private string RenderHeader() => $"""
    <div style="background: {PrimaryColor}; padding: 24px; text-align: center;">
        <span style="color: white; font-size: 24px; font-weight: 700;">Acme</span>
    </div>
    """;

// After (host your logo somewhere publicly accessible):
private string RenderHeader() => $"""
    <div style="background: {PrimaryColor}; padding: 24px; text-align: center;">
        <img src="https://cdn.yourdomain.com/logo-white.png"
             alt="Acme" height="32" style="display: block; margin: 0 auto;" />
    </div>
    """;

Adding a new template

Step 1: Add a value to the EmailTemplate enum in Domain:

// src/Acme.Domain/Enums/EmailTemplate.cs
public enum EmailTemplate
{
    // existing values...
    WeeklyDigest,
}

Step 2: Create the template class:

// src/Acme.Infrastructure/Email/Templates/WeeklyDigestTemplate.cs
public class WeeklyDigestTemplate : EmailTemplateBase
{
    private readonly string _userName;
    private readonly int _newProjects;

    public WeeklyDigestTemplate(string userName, int newProjects)
    {
        _userName = userName;
        _newProjects = newProjects;
    }

    protected override string RenderContent()
    {
        return $"""
            <h2 style="color: #1A56DB; font-size: 20px; margin: 0 0 16px;">
                Your weekly digest
            </h2>
            <p style="color: #374151; margin: 0 0 16px;">
                Hi {_userName}, here's what happened this week:
            </p>
            <ul style="color: #374151;">
                <li>{_newProjects} new project(s) created</li>
            </ul>
            """;
    }
}

Step 3: Add a case in ResendEmailService.SendTemplateAsync:

// src/Acme.Infrastructure/Email/ResendEmailService.cs
EmailTemplate.WeeklyDigest => new WeeklyDigestTemplate(
    model.UserName,
    model.NewProjects
),

Testing email rendering locally

Dump a template to HTML and open it in a browser — no SMTP server needed:

// Scratch: add temporarily to any endpoint or test
var template = new WeeklyDigestTemplate("Jane", 3);
var html = template.Render();
await File.WriteAllTextAsync("/tmp/weekly-digest-preview.html", html);

Then open /tmp/weekly-digest-preview.html in your browser. Delete this code before committing. For sends that actually went through, check the Emails tab in the Resend dashboard — it shows the full rendered HTML, delivery timestamp, and open/click events.

​Where templates live

​How templates work

​Changing the brand color

​Changing email copy

​Adding a logo

​Adding a new template

​Testing email rendering locally