Policy-Mandated Labels Such as "Adv:" in Email Subject Headers Considered Ineffective At Best

This memo discusses policies that require certain labels to be inserted in the "Subject:" header of a mail message. Such policies are difficult to specify accurately while remaining compliant with key RFCs and are likely to be ineffective at best. This memo discusses an alternate, \%standards-compliant approach that is significantly simpler to specify and is somewhat less likely to be ineffective. This memo provides information for the Internet community.