Sending test emails requires caution to avoid damaging the sending reputation of your production domain, as this can lead to delivery issues in the future. It's recommended to set up a dedicated test environment with its own sandboxed email sending to minimize the risk of accidentally spamming real customers with test emails. Testing locally or using a dedicated staging or development domain can also help catch broken assets and formatting issues before they affect your production delivery. When testing, it's essential to use valid email addresses on your own domain and avoid sending test emails to fake addresses or addresses that don't belong to you, as this can generate bounces and negatively impact your domain reputation. Tools like MailCatcher, Mailtrap, and MockSMTP provide dedicated email addresses or locally hosted tools specifically designed for testing in development and test environments, allowing you to simulate sending emails and troubleshoot issues before they reach production. Additionally, Postmark is introducing new features, such as a Test API Token for Account level functions, API error and bounce error generators, Sandbox email addresses, and the ability to demarcate certain servers as test servers.