Remove strict alignment (and adkim and aspf tags)

[seth@…]

Strict alignment is rarely deployed, doesn't provide additional security (especially if any cloud services are being used to send mail on behalf of the domain), and actually makes blocking all unauthenticated mail significantly harder, not easier due to confusion.

[todd.herr@…]

Valimail data:

73917 DMARC records examined

 1244 with adkim=r (default)
 1346 with adkim=s

 1856 with aspf=r (default)
 1505 with aspf=s

[todd.herr@…]

Proposed text to remove strict alignment references pushed to github and merged with main branch.

[mail@…]

dns probe on Tranco toplist 2021-05-09:

152348 v=DMARC1 records
 11049 with adkim=r (default)
  5934 with adkim=s

 18288 with aspf=r (default)
  6668 with aspf=s

 58405 v=DMARC1 records with (qurantine|reject) policy
  5339 with adkim=r (default)
  4707 with adkim=s

  7247 with aspf=r (default)
  5226 with aspf=s

[mail@…]

Whoops, sorry for changing the ticket status.

[smj@…]

Looking at the ~2.9MM valid DMARC records from the dataset Farsight provided to DMARC.org through 1Q2021, retrievable via DNS at that time.

Tag	Count
adkim=r	163,441
adkim=s	152,615
aspf=r	242,198
aspf=s	166,519

[todd.herr@…]

Consensus from the 27 May 2021 Interim session (​https://datatracker.ietf.org/doc/minutes-interim-2021-dmarc-01-202105270900/) was to leave the tags in place for now, but to include their use in a future discussion of "ratchet mechanisms" meant to provide Domain Owners a way to slow-roll DMARC adoption