It seems Outlook is totally bugged.
I set up a mail server and sent 4 emails in a row, for the first one Microsoft said:
dkim=pass (signature was verified)
For the second one it said:
dkim=fail (body hash did not verify)
For the third one it said:
dkim=timeout (key query timeout)
And then the 4th one passed again.
key query timeout may be forgiven (maybe Azure's internal DNS server is slow), but body hash did not verify If it cannot deterministically run a hash function, what can it do?
At this point I'm no longer surprised why most people use Gmail: There at least the basic tech works.
Click to expand the 4 `Authentication-Results` headers that `outlook.office.com` added
Authentication-Results: spf=pass (sender IP is 95.216.183.106)
smtp.mailfrom=mailserver3.aws.nh2.me; myoutlookdomain.com; dkim=pass (signature
was verified) header.d=mailserver3.aws.nh2.me;myoutlookdomain.com; dmarc=pass
action=none header.from=mailserver3.aws.nh2.me;compauth=pass reason=100
Authentication-Results: spf=pass (sender IP is 95.216.183.106)
smtp.mailfrom=mailserver3.aws.nh2.me; myoutlookdomain.com; dkim=fail (body hash
did not verify) header.d=mailserver3.aws.nh2.me;myoutlookdomain.com; dmarc=pass
action=none header.from=mailserver3.aws.nh2.me;compauth=pass reason=100
Authentication-Results: spf=pass (sender IP is 95.216.183.106)
smtp.mailfrom=mailserver3.aws.nh2.me; myoutlookdomain.com; dkim=timeout (key query
timeout) header.d=mailserver3.aws.nh2.me;myoutlookdomain.com; dmarc=pass
action=none header.from=mailserver3.aws.nh2.me;compauth=pass reason=100
Authentication-Results: spf=pass (sender IP is 95.216.183.106)
smtp.mailfrom=mailserver3.aws.nh2.me; myoutlookdomain.com; dkim=pass (signature
was verified) header.d=mailserver3.aws.nh2.me;myoutlookdomain.com; dmarc=pass
action=none header.from=mailserver3.aws.nh2.me;compauth=pass reason=100