Say I want a personal domain and have the MX not be Google or Fastmail, how complete is the implementation of these standards on major email providers' SMTP setups? Would I need to do thorough research or is it reasonable to expect it to just work in a, say, European SMTP hoster's configuration?
Any major ISP with clue is at least checking SPF, DMARC and DKIM scores on its incoming edge smtpd that talks to the world. How they use the scoring and results for spam filtering varies widely.
