PPTP GRE protocol problem

RouterOS Forwarding Protocols
1

Hi, i have problem with PPTP VPN , i think its something about gre protocol and nat

so what im trying to do is that my endpoint computers in network is connecting to remote pptp vpn (not microtik) and it ist stuck at “verifying your credential”
in connections i see that client is comunicating to VPN server but it not get any reply

pc client → Mikrotik —> ISP —> internet —> PPTP VPN server

i have no firewall rules, only 3 NAT rule

 0    ;;; Masquerade Public Traffic
      chain=srcnat action=masquerade src-address=10.10.10.0/24 
      out-interface=T-COM-ether1 log=no log-prefix=""

 1    chain=dstnat action=dst-nat to-addresses=10.10.10.9 to-ports=443 
      protocol=tcp in-interface=T-COM-ether1 dst-port=443 log=no log-prefix="" 

 2    chain=dstnat action=dst-nat to-addresses=10.10.10.9 to-ports=80 
      protocol=tcp in-interface=T-COM-ether1 dst-port=80 log=no log-prefix=""

i tried it without mikrotik, only client —> ISP —> PPTP VPN server and it is working
so it’s definitely problem in mikrotik.

Can anybody help me?

Thank you :confused: