[SwellJoe]

I would argue that this is at least partly because Postfix has a larger surface area...it does more, and thus, should reasonably be expected to have had a few more run-ins with security problems. Unless things have changed a lot over the past several years, qmail isn't capable of even functioning in a number of modern email environments, without significant patching.

Once qmail has been patched up to modern MTA standards, it no longer has the pedigree of being built and maintained by djb. I don't know the people who maintain the huge patch sets for qmail...maybe they're good. I know Wietse is more than competent.

But, that may be what you're getting at with "Postfix is the saner default choice for normal users". We support all of them (Sendmail, Postfix, qmail, and exim) in Virtualmin to varying degrees, but we configure Postfix, by default, and very strongly encourage its use over the alternatives (mostly because we know Postfix so much better, and because so many more people use it). About 95% of our users stick with Postfix, though we do have some users of all of the others.