SBS 2011 replacement: any traps?

Hello everyone,

i am planning to replace my SBS 2011. i actually only use AD, DNS/DHCP, WSUS, Exchange and the fileserver (all have the same permissions). Sharepoint and the rest of the SBS I don’t really use.
It is important that iPhones can receive emails from the public internet.
Are there any pitfalls that I have to be aware of?

thanks a lot in advance