I'm pretty confident that Dr Byte is correct in his statement. The rate calculation APIs are:

RateRequest
IntlRateRequest

They are not listed in the USPS notice email. Additionally, the email mentions:

Technical user guides available via: http://www.usps.com/webtools/technical.htm have been updated and denote proper URL prefixes.
If you read through the rate request documentation, you'll see that the server has not changed.

And one more point, I just signed up a new customer for API access, and the email still shows production.shippingapis.com as the proper server:

Thank you for contacting us. Your profile has been updated to allow you access to the Production Server.

1. The Production Server URL is: production.shippingapis.com.
2. There is a line of code that refers to "shippingapitest.dll". You'll need to remove the word "test".
Best regards,