Post Office Address Verification Enforcement

With the Post Office gearing up the enforce Address standards on May 1, 2009 - we're reviewing our current employee address information and finding cases where they aren't meeting the standard.  While we're training our staff to enter data the correctly, we also are building audits to catch entry errors.  Also, down the road we'd like to have employees enter their own addresses and address changes, so this will likely become a bigger issue.

I know there are address verification services that can be purchased, but we're under a budget crunch right now - so the question is

What do other companies do to make sure their addresses meet USPS guidelines?  "Free" is the key word here, but I'd like to hear about all methods of verification.