Here’s something I just learned: If you are running dma(8), /etc/dma.conf will contain MAILNAME. If your email server is somewhere else, but you set MAILNAME as your domain – dma will deliver locally.
I had /etc/dma.conf set with MAILNAME shiningsilence.com – so dma kept delivering overnight periodic results to root, which was aliased to email@example.com in /etc/mail/aliases and so it was delivered to ‘justin’ locally on the machine.
Changing MAILNAME to www.shiningsilence.com – the host you are reading right now – fixed the problem. Now, whether this was an automatically set config or something I misconfigured some years ago… I can’t tell.