RE: USPS Electronic PostMarks - Anyone using them

Jim, 

He's (she's?) probably referring to electronic postage, not EPMs. The
EPM is basically a datestamp from the USPS that can be used to
authenticate a specific document. You hash the document and send the
hash to them, they store the hash for 7 years and return a datestamp and
serial number. At a later date if there's a question about the
authenticity of a document you recompute the hash and compare it to
what's at the USPS.

-Walden