I am having problems with my Exchange Server since upgrading to Yosemite.

I have my Mac Mail / Calendar / Contacts apps set up with my Exchange server, and am also running an iPhone 5 and iPad 4.

I have Outlook 2011 for Mac also installed on my Mac Book Air.

The issues I have are as follows:

My iPad and iPhone work fine. New contacts can be added / existing contacts changed as can appointments. These all sync fine with my exchange server, and update on all my clients & devices.

I can add new appointments via my Outlook 2011 for Mac client, but cannot change existing ones. I can neither add new, nor change existing, contacts through Outlook.

My Mac Mail app will add new appointments and sync to Exchange fine, but will not allow me to change existing calendar entries.

My Mac Contacts app will not allow me to add new, nor change existing, contacts.

Mail works fine across all platforms & clients

I have progressed this as far as I can with Fasthosts (my domain registrars and email hosting company) and they can find no issues their end.

They believe it to be an issue between the latest OS Yosemite and my exchange server.

It's very frustrating - anyone else out there have the same issue or is it just me!?

J