A contact lookup finds no match because one phone number includes spaces and another does not. The obvious response is to clean every value aggressively. That can introduce a different problem: changing a valid identifier into the wrong one.

Normalization should produce a consistent representation while retaining the original input when there is a justified need to inspect it.

Separate normalization from validation

Normalization changes representation. Validation checks whether a value meets an expected structure. Neither proves that a person owns an email address or phone number.

A syntactically valid address can still be unreachable. A well-formatted phone number can belong to a different person. Treat ownership verification as a separate process.

Be careful with email addresses

Trim accidental surrounding whitespace. Normalize the domain according to a defined policy.…