Thanks for your reply.
The name servers set in the ISPConfig is not the same in the /etc/resolv.conf
is it normal?
This is the result of the Curl:
# curl -d "test" https://api-3t.paypal.com/nvp -v
* About to connect() to api-3t.paypal.com port 443 (#0)
* Trying 126.96.36.199... Connection timed out
* Trying 188.8.131.52... Connection timed out
* Trying 184.108.40.206... Connection timed out
* Trying 220.127.116.11... Connection timed out
* couldn't connect to host
* Closing connection #0
curl: (7) couldn't connect to host