Love the testing feature. Our team sends at a volume, transactional emails especially. Account, project, and team management testing features help us QA a bunch of templates in not time.
I switched to Mailcatch not long ago when I felt the need for better email testing. It gives me an instant view of email, which allows me to assess the progress and performance quickly.
One of the top things I appreciate about Mailcatch is its ease of use. The setup takes just a few minutes, and the interface is very intuitive and modern.