When GW client isn't already open we get the following error message when opening an EML file in Windows Explorer (Win7 64).
"There was a problem sending the command to the program."
The email ends up opening, you just have the annoying error dialog.
This seems to be DDE related as deleting the following registry key prevents the error from occurring:
I have not yet determined if there are any negative side effects of deleting the above mentioned key.
Does anyone have any detail on why this happens and what the best resolution would is?