Currently, if I copy any text from a RDP session (say SQL Server SSMS running on Windows Server 2008) and paste it into a Mac Mail message (Yosemite), the text is pasted as a .vcf file. This happens all of the time.
If I first paste the text into TextPad, copy or cut the text, then paste it into the Mac Mail message, the text pastes as expected.
This issue is, unfortunately, not new.
I am running a 2014 Mac Book Pro Retina 15".
I have configured my RDP session to have a resolution of 1680x1050, True Color (24 bit), and "Full screen mode" is set to custom with "Start session in full screen" and "Scale content" both checked. I also have "Connect to admin session" and "Forward printing device" checked.