Microsoft Exchange Question

I use Microsoft Exchange for my e-mail and calendar, however, it seems that when I add a contact on my phone it is not adding it to my Outlook program like it should. When I add a contact in Outlook it does sync to my iPhone.

I use 1&1 as my provider, is there any known issues with Exchange syncing? It used to work flawlessly now I don't know what's going on, any help would be greatly appreciated!