Alasdair Taylor's Answer

An anti-spam policy is a document that seeks to govern or control spam communications.

A policy will often begin by defining “spam”.  There is no universally agreed definition, but a typical definition will cover communications that are unlawful, unsolicited, commercial on some level and/or are made in bulk.  Under some definitions, communications do not need to be commercial to be spam; under other definitions, they do not need to be in bulk.  It depends somewhat upon the medium.

Some policies, particularly those taking a precautionary approach, will specify precisely the types of communication that are permitted.  For instance, an anti-spam policy used by an email marketing service may specify the exact means that must be employed by users to build email marketing lists.

A policy will usually prohibit all spam.  The prohibition may be contractual, such that a breach of the policy constitutes an actionable breach of contract.  Where an anti-spam policy relates to the provision of a service, a breach of the policy may have defined consequences, such as the withdrawal of the service.