[timsneath]

I don’t have canonical data to fall back on, but I suspect that DKIM and DMARC being set up are key to successful mail delivery these days, if you’re not using one of the biggest players like Gmail. I use Rackspace Mail for my personal domain (not the hosted Exchange variety) and with these two configured I’ve had no issues with mail delivery. But many mail hosting providers still don’t support DKIM: which is one reason I’m still relying on Rackspace despite all their broader woes.