I am going to assume that " DP & Exchange" actually means " DP 7 Exchange"
I found a couple of lab cases where this problem was reported as fixed in DP 7.03 patch bundle. I looked at the patch description, and did not see this problem listed, but, the 7.03 patch bundle does fix some other Exchange 2010 Integration problems, and this fix may just not be documented, so, if it is not already installed, and if you are indeed on DP 7, I would suggest that you get this patch installed