The reason why I don’t do unpaid support is because MaraDNS is an open-source project. Open source fundamentally changes the customer-supplier relationship; the thinking behind open source is that I supply something that benefits the community as a whole. The community, in return, benefits MaraDNS.
If I answer a private MaraDNS support email for free, I am not doing anything to benefit the MaraDNS community. I am only benefiting one particular user of MaraDNS.
MaraDNS users with support concerns should help MaraDNS by either paying me (which encourages me to work harder on MaraDNS), or by making their support concern public; this way any reply to their email is public and the next person with the same concern can quickly find the answer to their question in the MaraDNS mailing list archives.