2014 R2 Calendar Server Configuration

Just trying to get this working and not sure I have it setup right. Can this server install be on the same box that hosts Webmail and the MTA/GWIA or is it recommended to have it on it's own box or alongside another PO? Just trying to get an idea of best approach. I attempted to install it on the Webmail/MTA/GWIA box and not sure I got it working right. Went through all the configuration and it appears to be running (checked gwcalsvr service and it's running). When I go to my mac and attempt to add it manually under calendar accounts I get unable to verify account name or password. Might be something simple I am missing I hope.

Thanks for any help!