The identity of the sender of an e-mail message is verified by performing a plurality of tests on DNS information. The DNS information is based on a client IP address or a sender address. Each test performed has a corresponding intrinsic confidence value representing the degree of confidence the test provides of the sender identity relationship. If multiple tests are successful the test result with the highest confidence value of the hierarchy of confidence values is used. The confidence value is optionally used in subsequent identity tests as specified by the subsequent test.