How to open .EML files on iPad
Email file viewer app from Kupon B.G known as Klammer. That is available in Apple's App Store. It will open Outlook .msg files, standard .eml files, and also winmail.dat files on your iPad. 

First open email using the iPad's Mail application.  The file attachments were immediately visible in the email. 

To view the file attachments just simply touched the .eml file we wanted to view, pressing on it for a full two seconds.  iPad then opened a window asking us which application we wanted to use to open the file.  then choose Klammer

It will view .eml file immediately appeared rendered in full html formatting.
It is a very simple app  for opening .msg and .eml email messages.

Klammer is no longer a free app, it is now $0.99 USD.