Hi Guys,
I installed ROS 6.13 as a VM on my ESXi running version 5.5. I tried to get PPTP to work with my iPhone 5 for days without success - then I found this post:
http://forum.mikrotik.com/t/esxi-5-5-and-mikrotik-support-vmxnet3/70988/1
Turns out ESXi 5.5 had a bug that would drop PPTP traffic. After upgrading to 5.5 U1, I was able to connect.
W.