Hi everyone. I am selling quite a lot of digital products, using free WordPress plugin called Paid Downloads (works like a charm for paid automated downloads). Today I have received the email from PayPal, stating: In a bulletin dated the 18th of October, 2011, we announced that we were going to expand the number of IP addresses for PAYPAL to improve our site?s performance, scalability and availability. As part of this transition, we planned to discontinue support for HTTP 1.0 protocol starting the 7th of October, 2013. We have recently identified that this change may impact the ability of some of our merchants to perform IPN (Instant Payment Notification) post-back validation or PDT (Payment Data Transfer) posts to PAYPAL and ipnpb.p4yp4l.com. This happens when the IPN or PDT scripts use HTTP 1.0 protocol and do not include the ?Host: www.paypal.com? or ?Host: ipnpb.paypal.com? header in the HTTP request. Additional Details Starting the 7th of October, 2013, we will require all incoming requests to have a ?Host? header which complies with HTTP 1.1 Specifications. This header was not required under HTTP 1.0. IPN and PDT scripts using HTTP 1.0 may start failing with ?HTTP/1.0 400 Bad Request? errors after the 7th of October, 2013, which will result in IPN messages not being validated successfully, or PDT scripts not being able to retrieve transaction information. Action Required before the 7th of October, 2013 Merchants need to update their IPN and/or PDT scripts to use HTTP 1.1, and include the ?Host? and ?Connection: close? HTTP header in the IPN postback script. Example with Host as www.paypal.com (please make necessary changes if you are using ipnpb.paypal.com): ASP //Set values for the request back req.Method="POST"; req.Host="'www.paypal.com'"; req.ContentType="application/x-www-form-urlencoded"; Perl $req=HTTP::Request->new('POST', 'https://www.paypal.com/cgi-bin/webscr'); $req->content_type('application/x-www-form-urlencoded'); $req->header(Host=> 'www.paypal.com'); $req->header(Connection=> 'close'); PHP // post back to PayPal system to validate $header="POST /cgi-bin/webscr HTTP/1.1\r\n"; $header .="Content-Type: application/x-www-form-urlencoded\r\n"; $header .="Host: www.paypal.com\r\n"; $header .="Connection: close\r\n\r\n"; Java HttpsURLConnection uc=(HttpsURLConnection) u.openConnection(); uc.setDoOutput(true); uc.setRequestProperty("Content-Type","application/x-www-form-urlencoded"); uc.setRequestProperty("Host", "www.paypal.com"); uc.setRequestProperty("Connection", "Close"); The PayPal Sandbox has been configured to reject any HTTP requests without the ?Host? header with HTTP 400 error. Merchants can use the Sandbox environment to certify the changes to their IPN and PDT scripts. For more information on PDT and IPN, please refer to http://www.paypal.com/pdt and http://www.paypal.com/ipn. For additional information or questions about this change, please contact PayPal's Merchant Technical Support team via https://www.paypal.com/mts. Sincerely, PayPal As I am a totally coding noob, I do not understand if I should make something with the plugin, or with my PayPal. I am sure more of you guys are selling digital things here and for sure use this plugin, so if you can give me an advice what to do, I will be very happy . thanks!