We'd like to turn off their spam filtering and rely on a third party solution like https://www.cudamail.com/. We don't know anything about these services and I found Cuda Mail just by Googling for "Outsourced Spam filtering service"

Has anyone here used such a solution and, if so, which one seems to be the "best" that members of this community might recommend?

Aside - we can work around the problem for our own internal emails by simply forwarding emails to Gmail and relying on Gmail's filtering, however, our customer base is VERY un-savvy technically and we'd like a third party solution to simply solve this problem for our less technical users.

Any help or recommendations would be much appreciated. Thanks in advance!