We should eventually configure SPF DNS records for phabricator.org (none), phacility.com (Google Domains), and phabricator.com (SES). This would reduce an attacker's ability to create email which appeared to originate from the Phabricator system or our corporate accounts.
I think the risk here is very low and SPF is not trivial to understand and test, so I don't plan to do this anytime soon, although we should probably do it before we do anything with payments.