I just received this e-mail from Paypal:
"In a bulletin dated October 18, 2011, we announced that we were going to expand the number of IP addresses for www.paypal.com 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 October 7, 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 www.paypal.com and ipnpb.paypal.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 October 7, 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 October 7, 2013, which will result in IPN messages not being validated successfully, or PDT scripts not being able to retrieve transaction information.
Action Required before October 7, 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.

My question is: Do we need to do anything for our Symbiostcok sites? Will this change impact our symbiostock Paypal IPN?
Thanks in advance for any feedback.

are you sure this is not some sort of a scam? I have found the same text on the web but with different dates:

In a bulletin dated October 18, 2011, we announced that we were going to expand the number of IP addresses for www.paypal.com to improve our site’s performance, scalability and availability. As part of this transition, we planned to discontinue support for the HTTP 1.0 protocol starting February 1, 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 www.paypal.com. This happens when the IPN or PDT scripts use the HTTP 1.0 protocol and do not include the “Host: www.paypal.com” header in the HTTP request.

Additional Details Starting February 1, 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/1.1 400 Bad Request” errors after February 1, 2013, which will result in IPN messages not being validated successfully, or PDT scripts not being able to retrieve transaction information.

Your Action Required before February 1, 2013 You will need to update your IPN and/or PDT scripts to use HTTP 1.1, and include the "Host: www.paypal.com" and "Connection: close" HTTP headers in the IPN and PDT scripts.

it might still be legit but if it didn't break anything on February 1 2013, why would it now? and why was the date extended..

I have seen many forums discussing this issue.. some prior to February 1 2013, and some more recently with the new dates..

isn't HTTP 1.0 pretty old anyway.. I have a feeling that this warning is more like for "ancient sites" but I might be wrong..

https://www.paypal-notify.com/eventnotification/event_details_popup?eventId=2891

Its genuine