I’ve had trouble recently with using my email here at donkelly.net: some — not all, but some — networks wouldn’t communicate with mine, emails couldn’t be exchanged, and looking into why that was so, at say, SDF.org I found that they couldn’t even resolve my domain. The domain always resolved on my home computer though, so some DNS was working somehow.
But my laptop generally uses the DNS server on whatever wifi it’s connected to, and now, connecting here on Rainbow Lake, whatever DNS server they use wouldn’t resolve my domain — which I took to mean uh oh, there really is a problem with my setup and not just at SDF or whatever.
I checked my DNS info using third party websites and found that here were some major discrepancies — there were four nameservers listed rather than two, and two of them didn’t work. Turns out the original ones had been retired (by my service provider) but my system hadn’t been updated, and the broken servers were the retired originals, which were the only ones listed in my site’s configuration — I have no idea where/how the correct nameservers got listed. I went in and removed the bad servers, added the good ones to my configuration, gave it a few hours, and now even the formerly broken emails seem to work.
I could have, and should have, done something about this months ago.