I don't even bother writing people who are using gmail. For now, I filter based on their email address, but I might as well integrate an MX lookup in my MUA, so as not to be disappointed/depressed randomly with no obvious reason (until I manually check the MX record myself, that is).
@monsieuricon the subject does look spammy though.
@monsieuricon yeah... "mail can be proved to be send on behalf of someone responsible for the from address" and "mail contains information that the receiver has asked for or thinks is important enough to read" are entirely separate things.
With any luck dmarc et al might ensure some phishing or spam emails get marked as spam when they otherwise would have been missed (allowing someone to "protect" their own domain), but if you are actually sending unsolicited marketing email it certainly wouldn't do the opposite.
@monsieuricon that's kind of separate from the "Gmail not liking you" thing, which can get important emails that people actually want to read banished from the inbox :(