Review on GateScanner by Chucky Hepler

It was easy for me as an administrator to set up so our users could access it via their email clients without having to go through one more server than necessary or have any additional software installed locally.

The price point isn't bad either. I would say there are some things we don't support out of the box but they were quick enough at responding back when contacted by asking questions about what features/functionality did not work right away. We use this primarily because it works well across multiple platforms including mobile devices too.