At this point I'm not sure if this is valid or not.  I did get a voicemail from this number but the person identified herself as calling on behalf of the US Postal Service Every Door Direct.  It looks like it's a new service being marketed by the USPS.  However, I don't know (and don't have time to research it) whether this actually is the USPS calling, a telemarketer working in conjunction with the USPS, or a scammer just latching on.