Dragonfly Mail Agent (dma) in the base system

The Dragonfly Mail Agent (dma) is a small Mail Transport Agent (MTA)
which accepts mail from a local Mail User Agent (MUA) and delivers it
locally or to a smarthost for delivery. dma does not accept inbound
mail (i.e., it does not listen on port 25) and is not intended to
provide the same functionality as a full MTA like postfix or sendmail.
It is intended for use cases such as delivering cron(8) mail.

Since 2014 we have a copy of dma in the base system available as an
optional component, enabled via the WITH_DMAGENT src.conf knob.

I am interested in determining whether dma is a viable minimal base
system MTA, and if not what gaps remain. If you have enabled DMA on
your systems (or are willing to give it a try) and have any feedback
or are aware of issues please follow up or submit a PR as appropriate.