Before I get to the question I'll give you some info about our arcitecture.

We have 7 remote sites each with 5mb connections.

5-10 computer at each site

We are running exchange 2010 centrally from one server on a 20mb connection.

All clients are running windows 7 64bit with office 2013

We recetly upgraded from office 2003 to 2013 when this problem started.

If a user clicks on an attachment from one of our remote sites, and if the attachment is larger than 150kb the outlook client displays (not responding) for up to two minutes.  If you wait long enough the attachment will open without error.  It doesnt matter if its a word docuemnt, PDF, JPG they all respond the same.  There are several active application add-ins running I have not tried to disable  any of them yet.

Acrobat PDFMaker office com addin

Lync meeting addin for microsoft office 2013

microsoft exchange addin

microsoft sharepoint server colleague import addin

microsoft vba for outlook addin

onenote notes about outlook items

outlook social connector 2013

symantec endpoint protection outlook addin

I should also mention theres plenty of bandwidth free at both ends of the pipe.  Moving the same file size accross the network literally takes only takes a second or less.

How can I go about troubleshootng this issue further?

Has anyone else experieced this?

What have you done to fix it?