From: test <test@example.com>
Subject: test reply to UTF-16 encoded message
To: test2 <test2@example.com>
Date: Sat, 27 Feb 2016 17:11:45 +0100
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-16LE;
Content-Transfer-Encoding: base64

//5IAGkAIABNAGEAZwBuAHUAcwAsACAAaABlAHIAZQAgAGEAIABiAGUAdAB0AGUAcgAgAFUA
VABGAC0AMQA2ACAAZQBuAGMAbwBkAGUAZAAgAG0AYQBpAGwALgA=