1. Accept that the new standard is that ip addresses should be supported, and write a new rfc document with that change.
2. Encourage people to not support this.
Simply asking all mailservers to support this non-standard feature (or de facto standard) is arguable the worst outcome, because now every mail server implementer is expected to implement the standard + a bunch of institutional knowledge.
Luckily with mail there's a lot of incentive to set things up correctly, because getting parts of it wrong likely results in a higher number of emails going to spam.
1. Accept that the new standard is that ip addresses should be supported, and write a new rfc document with that change. 2. Encourage people to not support this.
Simply asking all mailservers to support this non-standard feature (or de facto standard) is arguable the worst outcome, because now every mail server implementer is expected to implement the standard + a bunch of institutional knowledge.
Luckily with mail there's a lot of incentive to set things up correctly, because getting parts of it wrong likely results in a higher number of emails going to spam.