Examples

john.smith@some.domain.com		a single email address
john.smith@		john.smith from any domain
@some.domain.com		any user from some.domain.com
abcdef		any address containing the sequence abcdef

Important    The order in which the lists are used in the filtering process is first white, then black. Scanning finishes when a given address is found or both lists have been scanned without finding it. If the address is found on the white list, the message is delivered to your mail box. If on the black list, it is discarded. If not found at all, the message is discarded and your "Response to unknown sender" is mailed out. If, for instance, john.smith@ is on the white list, and @some.domain.com - on the black list, then messages from john.smith@some.domain.com are delivered normally. But message from other addresses at the same domain are all discarded.