I encountered the following problem twice in the last month with PayPal IPN in live mode.
I receive an incoming IPN as usual, and all the data are correct. Then I append cmd=_notify-validate& and send the input to PayPal to verify it. The documentation says to expect VERIFIED or INVALID as response.
Instead those two times I got
<HTML><HEAD><TITLE>Error</TITLE></HEAD><BODY>
An error occurred while processing your request.<p>
Reference #…
</BODY></HTML>
with HTTP status 503. My script of course dismisses the IPN, but how should I handle this?
Normally, if the listener fails, PayPal retries to notify in an increasing interval. But I don’t receive any additional IPNs. I could save the request and verify it later on my own, but for how long does this work? I assume I have to verify it instantenously, otherwise PayPal will forget about it.
Can anybody recommend a good way of handling this?
