I've send this question to developer.support@nokia.com but only got a link to the FAQ and got asked to post my question here again. So here it goes:

Dear Developer Support Team,

we're using Symbian/Qt IAP with our own backend server. There we use the Ticket Verification API to test the purchase tickets. We directly pass the purchase ticket from our app to the backend server and from there to Nokia IAP servers. We don't extract or manipulate the contents of the purchase ticket.

If we're using the app in online testing mode everything works fine. The Ticket Verification API accepts our POST request and we receive a valid response. But if we remove the "TEST_MODE.TXT" file in order to use the IAP API in production mode, the Ticket Verification API returns "HTTP 400 - Bad Request".

The code paths in our app and the backend server are exactly the same in both situations. The only difference is the existence of the TEST_MODE.TXT file.

So my question is: Is there anything else we need to do in order to use the Ticket Verification API in production mode? E.g. must our app be published? Or do we have to use a different server address?

Here is one transaction-ID that shows this problem: 218558590949

If you need more information please don't hesitate to contact me.

Best Regards,
Cornelius Hald
*EDIT*
Please also not that the money has been successfully withdrawn from my Credit Card.