When I use PayPal sandbox with PayPal IPN - error 503

[andrewk333]

I am using PayPal sandbox with PayPal IPN. I am sending notifications to a blank page with HTTP 200 OK header sent in the PHP code.

While I should at least get that 200 back, I always get 503 (service unavailable) error. Is this a problem with the PayPal sandbox or something??

[andrewk333]

Could it also be a problem with security and like cross domains not allowed for whatever reason? Is there anything additional I have to do?

[slawkens]

Refresh.

Many of my customers have this problem.

The IPN returns 503, however in script nothing was changed.

So it came out of nothing. Happening since last month or so?