Sending custom emails in WordPress. Visit blog post https://bit.ly/2xlZG9L

send_email_actions.php

<?php

  add_action('wp_mail_content_type', function() {

    return "text/html";
  }, 10, 1);

  add_action('retrieve_password_message', function($message, $reset_key, $user_login, $user_data) {

    $logo_url     = esc_url('https://cdn-domain-name.com/assets/img/logo.png');
    $featured_url = esc_url('https://cdn-domain-name.com/assets/img/featured-image.png');
    $reset_url    = esc_url(home_url('/wp-login.php?action=rp&key=') . $reset_key . '&login=' . $user_login);

    compose_email(
      array(
        'title'   => __('Password reset requested.', 'textdomain'),
        'content' => html_entity_decode(sprintf(esc_html__('<p>%1$s,<strong> ' . $user_data->display_name . '</strong></p><p>%2$s</p><p>%3$s<br />'. $reset_url . '</p>'),
            __('Hi', 'textdomain'), // 1
            __('You have requested a password reset! If this was a mistake, just ignore this email and nothing will happen.', 'textdomain'), // 2
            __('To reset your password please click on the button bellow or copy &amp; paste the link to enter your new password', 'textdomain') // 3
        )),
        'logo_url'           => $logo_url,
        'featured_image_url' => $featured_url,
        'cta_button_url'     => $reset_url,
        'cta_button_text'    => __('Reset your password', 'textdomain') 
      ),
      $user_data->user_email
    );
  }, 10, 4);

  add_action('wp_new_user_notification_email', function($email_data, $user) {

    $reset_key    = get_password_reset_key($user);

    $logo_url     = esc_url('https://cdn-domain-name.com/assets/img/logo.png');
    $featured_url = esc_url('https://cdn-domain-name.com/assets/img/featured-image.png');
    $reset_url    = esc_url(home_url('/wp-login.php?action=rp&key=') . $reset_key . '&login=' . $user->data->user_login);

    return overwrite_email(
      $email_data, 
      array(
        'title'   => __('Welcome to Company Name!', 'textdomain'),
        'content' => html_entity_decode(sprintf(esc_html__('<p>%1$s,<strong> ' . $user->data->display_name . '</strong>%2$s</p><p>%3$s</p><p>%4$s<br />' . $reset_url . '</p>'),
            __('Hi', 'textdomain'), // 1
            __('and thank you for joining us!', 'textdomain'), // 2
            __('You have successfully registered an account.', 'textdomain'), // 3
            __('Click on the button bellow or copy &amp; paste the link to veriy your email address and enter your new password.', 'textdomain') // 4
        )),
        'logo_url'           => $logo_url,
        'featured_image_url' => $featured_url,
        'cta_button_url'     => $reset_url,
        'cta_button_text'    => __('Reset your password', 'textdomain') 
      )
    ); 
  }, 10, 2);