MailCoat is a fake SMTP service for developers to inspect and debug email samples. It's a completely free email service where messages never get delivered.
MailCoat is mostly useful for app development. Instead of configuring a real email account for sending emails, your application can use it for message delivery. You get the same experience as using any other email service provider, you can configure it as an outbound mail server and send your transactional or marketing emails through the MailCoat service. Unlike real email services MailCoat only accepts mail for delivery but never actually delivers anything. Instead, all the messages will be forwarded to your mailbox.