Sender Policy Framework

Description

The new spec can avoid to require backtracking. Specifically, because a domain-spec can include forward slashes, and because some of the terms allow cidr masks after a domain-spec, one has to support backtracking.

Rationale

As a general rule backtracking grammars is not good for untrusted input.

Details

Perhaps it would have been wise to have included a %-encoded forward-slash, as was done for spaces.

Backward compatibility

This change is not backward compatible.