I'm in 2.6.0 and it's greyed out on a workstation that has Outlook 2013 installed and other applications can launch it with their mail features. I have the "Documents: E-mail" user feature set.
On another workstation without a suitable email client the option is enabled (same user, myself) and summons the mail dialog, but when I try to proceed I then get an error dialog "There is no email program associated to perform the requested action. Please install an email program or, if one is already installed, create an association in the Default Programs control panel."