.msg file attachment in pdf

I work in the federal goverment. We used to be able to open internally hosted online pdf forms with .msg attachments until recently. Now we get the followingmessage "the file type you are adding cannot be opened or saved from adobe acrobat due to your Trust Manager settings for PDF file attachments and portfolio files if you trust this click ok"   We can click ok and attach the file but cannoty open it. When we try to open it we get "adobe acrobat cannot open teh file attachment because your PDF file attachment settings do not allow this file type to be opened".  What registry setting could we enable to allow .msg files to be opened?