User cash and paypal problem

Hello, we have a SERIOUS problem with user registration!

We get emails from paypal that new user has paid with Transactionscode and price. But this payment is not in transaction in admin-cp and the new user is not registered!!!

Now we also get warnings from paypal that our IPN domain is wrong. Our IPN-domain is:

https://mydomain.com/payment/post.html?gateway=paypal

but google send us another domain?

What is wrong?

Please help, it's urgend!!

Can nobody help us?

Has Paypal explained which IPN domain the money goes to? Your website may be hacked.
Flynax support can answer this, but it seems dead from them regarding this issue.

Hello Rune Hansen,

yes, paypal has explained to which IPN domain the money goes. Our website is not hacked. It's maybe leftovers from update.

Nice, that Flynax support can answer this, but they do not.