Note that as more senders use mail service providers, comprehensive blocking of all SPF records may have considerable collateral damage.<p>Whether you consider this good or bad may vary:  it means MSPs have a valid claim that senders exercise Good Citizen practices on <i>all</i> mailings, not just those circulating via the MSP.<p>Then there are the major players.  Yahoo&#x27;s been a freaking PITA for years on <i>outbound</i> spam (both spam and joe-job bounces), with no effective reporting mechanism.  Gmail&#x27;s been largely better IME, other providers vary.