Exchange migration and outlook problems

Hi all!

I`ve just completed migration from Exchange 2007 to Exchange 2013 CU9.

We have really huge problems with outlook 2013 clients all of them are on latest version.

Problem is, that performance is really terrible. Tried with HTTP/RPC and with MAPI, same thing.

OWA works just fine and is super fast. I don`t know what I did wrong during migration but we can`t use Outlook, or better said, we can but on local network or outside of company performance is really crappy...

I cheched certificates, DNS, autodiscover all seems to be in order.

Any idea where to start troubleshooting?

BR,

Greg