We have a production IIS / aspx e-commerce system in place that processes PayPal payments and about 10% of the time when we try to confirm with PayPal the received IPN message, we get an INVALID response.
The cause is that we are receiving some russian, french or some other foriegn language characters in the body of the IPN message (i.e. first name), and when we try to send that received IPN message back to PayPal, the "encoding" is somehow not preserved and a strange character gets sent back thereby resulting in an INVALID response.
I read somewhere to verify what the character encoding is and to preserve it when the IPN message is sent back to PayPal for verifiation.
Question - How do I determine what the inbound character encoding is when the IPN message comes in and how to set it properly to send a response back to PayPal.