SMTP Bucket is described as 'A web based fake SMTP server for e-mail integration testing' and is an website in the development category. There are more than 10 alternatives to SMTP Bucket, not only websites but also apps for a variety of platforms, including Windows, Linux, Mac and BSD. The best alternative is MailHog, which is both free and Open Source. Other great sites and apps similar to SMTP Bucket are Papercut, smtp4dev, FakeSMTP and Origami SMTP.
Dummy SMTP server that sits in the system tray and does not deliver the received messages. The received messages can be quickly viewed, saved and the source/structure inspected. Useful for testing/debugging software that generates email.
Origami SMTP was created with the idea to have a fake email server for testing purposes that supported TLS. This is because the code the developer was working on at the time had several hard coded values enforcing TLS so most other solutions would not work.
MailCatcher runs a super simple SMTP server which catches any message sent to it to display in a web interface. Run mailcatcher, set your favourite app to deliver to smtp://127.0.0.1:1025 instead of your default SMTP server, then check out http://127.0.0.