[deepstack]

>> Almost none of the things linked there are run by serious isps that are responsible for other peoples' mail in quantities of tens of thousands of inboxes or more.

If you look at Haraka in the list, it is used by craigslist to deliver a lot emails every day, they switched to it from postfix to save cost.

I know Haraka is smtp only, however by using ZoneMTA like what wildduck is using, it will be a complete email solution.