DKIM
DKIM these notes relate to how to setup DKIM and install it in relation to accounts which go through Google Gmail.
v=spf1 include:_spf.google.com -all
DKIM check example
google._domainkey.website-doctor.com
Paste the above into https://mxtoolbox.com/ and you can check DKIM.
This is what a dmarc policy looks like.
v=DMARC1; p=reject; rua=mailto:postmaster2@website-doctor.com, mailto:dmarc@website-doctor.com; pct=100; adkim=s; aspf=s
_dmarc