I've added my Endicia account but when I try to save i get the following error:
ZIP4 Data Value too large
Endicia changed their API so older versions of the app, pre 1.65, need to be upgraded.
Upgrade to the latest version of the Multi Carrier app by following this link and clicking on "Get it now".
You should receive an email once the upgrade has completed. You are then ready to try to add your account again.