We faced terrible Outlook 2010 performance on all our terminal servers after we upgraded to Exchange 2013. In Our case it was because we were running Office 2010 SP1 x86 Once we upgraded to Office 2010 SP2 , the issue was solved. In addition you may need to look at this as well http://blogs.technet.com/b/samdrey/archive/2014/10/30/outlook-in-online-mode-on-windows-7-is-slow-connecting-to-exchange-2013-a-blog-post-from-macster-and-sharing-from-festivalman-thanks-guys.aspx Hope this helps.