One of my clients just forwarded this to me...

In May, the U.S. Postal Service (USPS) will implement the new Rates in
accordance with the Federal Register, to adjust postage prices to cover
operational costs and respond to changes in the marketplace. With this
change, the USPS Web Tools will release new version iterations and
corresponding XML schemas for the APIs: domestic rates, international
label and custom forms APIs.

The international APIs: Global Label Express Mail, Global Label
Priority Mail and Global Label Airmail Parcel Post will be realigned to
three new services: Express Mail International, Priority Mail
International and First Class Mail International. Within these
services, two new service types, Express Mail International Flat Rate
Envelope and Priority Mail International Flat Rate Box will be added to
the Web Tools international APIs.

The Domestic Rate API V2 will be modified and can be used after the
release of Rate V3 for other than Large Priority Mail pieces.

A staging environment will be available in early April. Updated user
documentation will be posted on USPS.com at
http://www.usps.com/webtools. Please look for a follow-up email in
early April notifying you of specific dates and detailed information.

Are there any changes I need to worry about?

Cheers!

Chris