Installed, started and then realized that you have to give them your credentials so their server can download your mail rather than the app doing this. I understand the benefits of these cloud mail checkers but this is just a 'no go' for me. Too bad.
OAuth is implemented for products that support it, such as Google and Gmail accounts. Exchange doesn't support OAuth. See https://www.acompli.com/privacy-policy/.
That wouldn't change anything for me/us as they would still have access to my private mail which bothers me and/or access to my company mail which I'm sure bothers my company.