That file is required by your source, it handles sockets and encryption,
Unless you the references of it in Native.cs...
But if you remove the lines that reference 'libeay32.dll' I'm pretty sure your source will stop working..
It sounds like you tried to 'tidy up' your source files and deleted this file.
Add libeay32.dll in Source/Bin/Debug and in Source/Bin/Release