We do cleanse your addresses in order to optimize for maximum deliverability. All US addresses will be automatically standardized, cleansed, and verified through our CASS-Certified Address Verification system before being returned back to you in the API response. All international addresses will simply be standardized by being transformed to all uppercase. Afterwards, postcards and letters will be run through NCOA (National Change of Address) and CASS, as these are requirements for sending with USPS. This may result in the final mailing address being different from the ones you see in your API requests and Dashboard.