The site was unfortunately down for a few months due to a server upgrade. My service-provider changed hardware and virtualization-platform, so I decided to install the site on a new, up to date Linux distribution. At the same time, I had a lot going on in my private life, so there was simply not enough time to work on this. As a result, the site, along with my primary email server, was off the net for quite some time.
Now the services are restored, and hopefully, the site willl be running without interruptions for another decade or two.