I created this for a project that I was working on. Hopefully it will be helpful to others.
You need to sign-up for a free account at https://www.easypost.com/ in order to generate your own key. It also requires the base64 udf
#include "base64.au3"
#include "easypost.au3"
#include <IE.au3>
Global $rate
Global $login = ":" ; Enter your own key here
$from = _getaddress("Test Person", "1234 John Green RD", "", "North Preston", "NY", "14837", "US","1234567890")
$to = _getaddress("Test Person", "1234 Johnson Road", "", "North Preston", "NY", "14837", "US","1234567890")
$parcel = _getpackage("Parcel", 24)
$shipment = _getshipment($to, $from, $parcel)
$label = _getlabel($shipment, $rate)
If StringLen($label) > 200 Then
MsgBox(0, "", "Some Kind of Problem")
Exit
EndIf
_IECreate($label)
easypost.au3