From my experience with getting packages shipped through DGM SmartMail expedited shipping the DGM SmartMail expedited shipping is where the seller or shipper ships the item using DHL.
Then DHL handles the package for awhile until they eventually hand the package off to USPS who then delivers the package to your door or mailbox.
The DGM SmartMail expedited is not really expedited and takes longer in my experience than UPS, FEDEX or even USPS.
It's just a cheaper method for the seller or shipper of the package to send the package to you.
A lot of sellers on ebay use DGM SmartMail expedited to ship cheaper and smaller packages to buyers but it can be frustrating for some people waiting on those packages.
However most times it's packages I order that ship through DGM SmartMail expedited shipping that I'm in no hurry to get.
So I really don't care too much if they do use the DGM SmartMail expedited shipping as long as I get the package.