Connect to PPTP over Softether

[SoftGuest]

Hello, from the client (Windows PC) I need to establish a connection to server A running SoftEther and then through this connection I need to connect to Server B using PPTP protocol. Client and server A are under my control, server B is not.
I tried basic softether VPN set up with Virtual NAT; connection has been successful, the public IPv4 address of the client got changed to that of the server A.
However, trying to establish PPTP session after that results in connection time-out.
I thought that since SoftEther is L2 it could encapsulate GRE packets (used by PPTP). Maybe there's something I can do to achieve this. Also I'd appreciate if you can suggest any other solution even if it is a bit off-topic and uses other software/protocol.

P.S. Please do not advice getting rid of the PPTP protocol, for now it is not possible for me.

[solo]

Try the following steps:

1. on server A set DisableKernelModeSecureNAT = 1 and restart it
2. from server A connect to B with PPTP and test ping to B's subnet
3. connect a SE client to server A
4. from the client ping B's subnet

A, vNAT, B and the client must be on unique subnets.

[SoftGuest]

Try the following steps:

Hi solo, thanks for your kind cooperation and sorry about the late reply.
This is a bit different from what I was looking to achieve.
What I really want is to be able to connect to arbitrary PPTP servers from the client computer without accessing the server running Softether (B) each time or connecting to the PPTP from the server B.

[solo]

The above steps are meant for a diagnostic test, not daily connection routine. Just do it once and it may dawn on you that everything works fine.