The default policy scripts perform recipient and domain validation, authorize users, protect against directory harvest attacks and other such policy-related actions.
The intended use case is to create policy suitable for a receiver domain accepting mail for a smaller set of recipient domains. For example, a company such as Yahoo has millions of users for which it accepts email, but only a handful of domains.
This default policy assumes that you will configure the
relay_hosts option as
0.0.0.0/0, and that one of the two following actions is taken:
relay_domainsis defined as the set of domains you want to accept mail for (for all recipients in those domains).
You do not set
relay_domainsto anything, and instead set up a datasource query to validate the full email address of each individual recipient