Your CRM should support desktop operating systems, as well as the mobile ones preferred by your employees. Besides, they have to be equally supported. I mean, their interface along with functionality should be the same over desktop platforms, be it macOS or Windows. Certainly, mobile versions will differ from desktop ones but, nevertheless, they should feel and look the same when running on iOS and Android. In another case, your employees might need re-training. Besides, such a requirement can help you to distinguish a good quality CRM service from a poor one.