… until it stops moving

Nothing is impossible to kill. It’s just that sometimes after you kill something you have to keep shooting it until it stops moving.Mira Grant, Feed

It’s getting to the time of year when I can get away with some horror movie metaphors. Today, things that are dead.
1. ADSP
ADSP was a domain repudiation scheme that should never really have lived, but thankfully it’s now dead. If you see “_adsp._domainkey” in DNS somewhere, kill it with fire.
(Don’t confuse it with DMARC, it’s much improved spiritual successor.)
2. SenderID
SenderID was a slight variant of SPF created by Microsoft and pitched for a while as “SPF version 2”. If you see “spf2.0/” in a DNS TXT record, beat it down with a shovel.
3. DomainKeys
DomainKeys served valiantly as a prototype, but has been entirely replaced by it’s successor, DKIM. Nobody is paying any attention to DomainKeys signatures, certainly not for mail that’s also signed with DKIM.
It’s dead. Completely dead. So if you see “DomainKey-Signature:” in an email somewhere, shoot it until it stops moving.