Improvement send emails
Support webhooks to handle email bounce or invalid
https://yourdomain.com/mailgun-webhooks/unsubscribes: Handle when user press unsubscribe in mailgun. The user will be updated to uncheck receive admin emails, email on conversations.
https://yourdomain.com/mailgun-webhooks/permanent-failure: Handle when mailgun cannot send email to user. The user will be mark as email bounce state