Sure, as a good admin he should certainly implement all industry best practices.
Of course, once he did that he’d still have the same fucking problem as unless he convinced the rest of the world to drop SPF the relayed messages would still be rejected.
Honestly if anything he should focus on creating a solution where he can have DKIM active. He has dmarc and SPF, but not DKIM.
Sure, as a good admin he should certainly implement all industry best practices.
Of course, once he did that he’d still have the same fucking problem as unless he convinced the rest of the world to drop SPF the relayed messages would still be rejected.