If you do not have a USPS webtools ID in your SellerCloud account then the address validation can be done by Dazzle once the label information is pass from ShipBridge to Dazzle for printing.
Keep in mind that in order to enable address validation in Dazzle will result in failure to update your orders shipping status and tracking information in SellerCloud unless the following steps are taken:
Open Dazzle and select Preferences from the Menu
Select adress verification tab from Preferences and options window and click on the "Advanced" button.
Be sure to check the box next to the option called "Silent Mode". This is required because otherwise dazzle will require you to click "OK" after each address verification, preventing data from being sent back to ShipBridge.
Note: once you have a API credentials in your company settings under Shipping Rate API then you can disable Dazzles verification service altogether by selecting the radio button next to "None" in the section titled "Method" in the image from step 3 (above).