iPhone can connect to Microsoft Exchange Server with ease. Please follow the steps:-

Exchange Server Configurations

1 Outlook Web Access (OWA) must be enabled
2 Enable Exchange IMAP Support also
3 Enable RPC over HTTP for Exchange Server
4 No Digital Certificate configurations are required.

iPhone Configurations

1 - GoTo the Mail icon –> Others –> Exchange Button
2 - Enter the name and email address
3 - In the incoming server
     i) if you use OWA, enter that address (eg:- exchange.domain.com)
     ii) Otherwise, enter the  ”rpc over http” URL ( NO HTTPS)
4 - Enter the Exchange UserName and Password
5 - Enter the Incoming Server Name for SMTP
6 - leave the user and password blank for SMTP

Now Your iPhone is ready to Pull emails from Exchange Server.