For 10 years I have been smoothly using Paypal IPN to receive IPN messages from PayPal. However beginning the past 2 months (Jan / Feb 2016), and especially this month (Feb 2016), it has errors approximately 20% of the time! The specific error is: -PayPal IPN sends messages to my endpoint (a php script) with POST data successfully; -my script returns the POST data successfully; -but although 80% of the time, PayPal returns VERIFIED successfully, 20% of the time, it returns a Server 500 error (formerly happened only 1 out of 1,000 times for 10 years). (It does NOT return INVALID; it actually returns a Server 500 error). Thus my side cannot reliably verify incoming PayPal IPN messages reliably anymore, beginning this month. My reference is here: https://developer.paypal.com/docs/classic/ipn/integration-guide/IPNIntro/ As a workaround, I have begun assuming all POST data is valid even though it never gets the VERIFIED result, and double-checking the validity soon afterwards using something along the lines of curl -s --data "[credentials from https://www.paypal.com/us/cgi-bin/webscr?cmd=_profile-api-signature]&METHOD=TransactionSearch&STARTDATE=2016-02-23T00:00:00Z&VERSION=94" https://api-3t.paypal.com/nvp
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