PHP script processing Paypal IPN payments stopped working

Question

Two weeks ago my IPN payments processing PHP script triggered a 503 error and PayPal send an email I have to fix my script. As I didn't touch it for a long, long while I was wondering would went wrong.

I started debuging and at first there where no errors whatsoever, but then I also got 503 errors. I contacted the support team. They gave the default answers like use the trim function and curl. I even updated my code to their newest example solution (which is missing the use of the trim function).

So what's wrong? Why is the script working only occasionally?

NOTE: I know, that the questions is not very precise, but I hope it contains enough key words as I ask it for documentary reasons as I will answer it myself.

Answer 1

The reason was rather obvious. It had to do something with my server. I use Strato, a professional company so I didn't suspect them at first, but a google for 503 strato led to the solution. It is a security feature at Strato which can be turned off, but is on by default. I really wonder, why it didn't fire earlier, but this is how you can turn it off.

• log into your account
• choose your package
• go to Security (Sicherheit) in the menu
• choose ServerSide Security
• turn off Filter agains guestbook spam (Filter gegen Gästebuch Spam)

I hope this saves some of you the trouble of going through your scripts. Try this first if you have 503 errors.