A Permit Sonoma address and road name letter is the only way your new address number or road name will legally be recognized. Without this letter the post office will not provide mail service. Utilities will not allow for connections for service. Your property will not show up in the 9-1-1 system. Even the accessors office will not change your address for the parcel. If you need assistance, please contact the Customer Service Division of Permit Sonoma.