> On email systems that allow for 'subaddressing' or 'detailed addressing' (e.g., "ken+sieve@example.org"), This rfc merely acknowledges that some systems do t

> On email systems that allow for 'subaddressing' or 'detailed addressing' (e.g., "ken+sieve@example.org"), This rfc merely acknowledges that some systems do this. It doesn't say the must or even should.