Configuring Email Templates

AuthBox separates email delivery from email content.

The EmailProvider is responsible for sending emails, while the EmailTemplateConfig trait generates the email subjects and bodies used throughout the authentication workflow.

This separation allows you to change your email branding and messaging without modifying how emails are delivered.

Responsibilities

EmailTemplateConfig is used to generate:

• Email verification emails
• Password reset emails

Each template receives the authenticated user and any required token, allowing personalized messages and application-specific URLs.

The EmailTemplateConfig Trait

Implement the following trait to customize email content:

#![allow(unused)]
fn main() {
pub trait EmailTemplateConfig<U: AuthUser> {
    fn verify_email_subject(&self, user: &U) -> String;

    fn verify_email_body(
        &self,
        user: &U,
        token: &str,
    ) -> String;

    fn reset_password_subject(&self, user: &U) -> String;

    fn reset_password_body(
        &self,
        user: &U,
        token: &str,
    ) -> String;
}
}

Trait Methods

verify_email_subject

Returns the subject line for email verification messages.

#![allow(unused)]
fn main() {
fn verify_email_subject(&self, user: &U) -> String;
}

verify_email_body

Returns the body of the email verification message.

#![allow(unused)]
fn main() {
fn verify_email_body(
    &self,
    user: &U,
    token: &str,
) -> String;
}

reset_password_subject

Returns the subject line for password reset emails.

#![allow(unused)]
fn main() {
fn reset_password_subject(&self, user: &U) -> String;
}

reset_password_body

Returns the body of the password reset email.

#![allow(unused)]
fn main() {
fn reset_password_body(
    &self,
    user: &U,
    token: &str,
) -> String;
}

Example Implementation

#![allow(unused)]
fn main() {
#[derive(Clone)]
pub struct MockTemplates;

impl EmailTemplateConfig<TestUser> for MockTemplates {
    fn verify_email_subject(&self, _: &TestUser) -> String {
        "Verify your email".to_string()
    }

    fn verify_email_body(
        &self,
        user: &TestUser,
        token: &str,
    ) -> String {
        format!(
            "Hello {},

Please verify your email by clicking the link below:

http://localhost:8080/verify-email/{}

If you did not create this account, you can ignore this email.",
            user.email,
            token
        )
    }

    fn reset_password_subject(&self, _: &TestUser) -> String {
        "Reset your password".to_string()
    }

    fn reset_password_body(
        &self,
        user: &TestUser,
        token: &str,
    ) -> String {
        format!(
            "Hello {},

You requested a password reset.

Reset your password using the link below:

http://localhost:8080/reset-password/{}

If you did not request this, ignore this email.",
            user.email,
            token
        )
    }
}
}

Personalizing Emails

Because each method receives the authenticated user, templates can include personalized information such as:

• User name or email address
• Verification or reset links
• Company branding
• Support contact information
• Localized content
• HTML or plain text email bodies

For production applications, replace the example URLs with your application’s frontend or API endpoints.

Design

AuthBox intentionally separates responsibilities:

This design provides several benefits:

• Clean separation of concerns
• Easy branding customization
• Localization (i18n) support
• HTML or plain-text templates
• Ability to switch email providers without changing templates

Summary

• Implement EmailTemplateConfig to customize authentication emails.
• Templates are used for email verification and password reset workflows.
• The authenticated user and token are available when generating email content.
• Email templates are completely independent from the configured EmailProvider.
• Works with any supported email provider, including SMTP, SendGrid, Resend, or your own custom implementation.