Miva Store Owners Alert:
If you have gotten feedback from client that your USPS tracking links are not working correctly, they are right. In July of 2014 USPS changed the URL for their tracking page, so the default URL in the backend of Miva is not working correctly.
Here is the fix:
You can manually change the shipping link URL in admin on the domain settings page.
Go to domain settings > Shipping Tracking Links tab. Click on the edit here button for USPS and replace http://trkcnfrm1.smi.usps.com/PTSInternetWeb/InterLabelInquiry.do?origTrackNum=%tracknum% with https://tools.usps.com/go/TrackConfirmAction.action?tLabels=%tracknum% and click update.
Let us know if this fixes it for you.