I was working in one project in my current company it does a good job of detecting and blocking phishing attempts, malicious links, and suspicious emails before they reach the inbox. The setup and onboarding were fairly straightforward, and there are plenty of resources available if you need help understanding a feature or configuring a policy. Review collected by and hosted on G2.com.
The main thing I would improve is the user interface. There are quite a few settings and options, and it can take some time to find exactly what you need or understand how certain policies work. Some parts of the administration could be more intuitive and easier to navigate. Performance has generally been good, but the overall experience could be simpler for administrators. Review collected by and hosted on G2.com.