Verification of Mailing Addresses

Whenever you send a mailing through Lob, you reap the benefits of accurate address cleansing and verification powered by our CASS-Certified Address Verification API. Verifying addresses is a necessary part of sending mail at scale to optimize the efficiency and accuracy of your mail delivery.

Standardization and Verification

Upon creation, all US addresses will be automatically standardized, cleansed, and verified through our US Address Verification API before being returned back to you. All international addresses will simply be standardized by being transformed to all uppercase to conform with USPS standards.

Strictness Settings

Depending on what business logic you'd like to take based on your verification result, you can toggle your US Address Strictness Settings in your Dashboard. There are 3 possible Strictness Levels:

  • Strict: Only US addresses that Lob and the USPS deem deliverable can be successfully used as the to address for postcard, letter or check resources. Postcard, letter, and check requests sent with non-deliverable addresses will return a 422 (Unprocessable Entity) error. If addresses have never been run through verification (i.e. were created in the past), they will also err when used as the to address.

  • Normal: Postcards, letters, and checks will be created for addresses that Lob and the USPS deem deliverable, as well as addresses for which secondary information is extraneous or missing. Otherwise, you will receive a 422 (Unprocessable Entity) error. If addresses have never been run through verification (i.e. were created in the past), they will also err when used as the to address.

  • Relaxed: All postcard, letter, and check resources will be successfully created and mail delivery will be attempted, regardless of address validity. You will not receive a 422 (Unprocessable Entity) for Address Strictness reasons.

Ultimately, this allows you completely control the destiny of your final pieces. Only want to send to addresses that are guaranteed to be deliverable? Pick "Strict" mode. Confident that your addresses are right and want us to mail them out anyway? Use "Relaxed" mode. We want to give you the power to decide when Lob should be sending mail or when we should be rejecting based on deliverability. Ultimately, this reduces the amount of undeliverable mail you send and saves you money.