… but I did not touch the registry. OK, enough with the singing, my server doesn’t have a registry anyway! (at least not the one known from a certain operating system)
I DID however manage to mess up the configuration of my SMTP daemon. Sure, you might say that that is not a first, as I managed to inadvertedly disable TLS support a few months ago, but this time it was actually serious enough to be able to cause mail loss on my end. I noticed it this morning as I received a ‘delayed’ delivery alert from my MTA telling me that it had trouble delivering a reminder I had sent to myself. Looking a little further, I found the server trying to look up the domain in DNS and subsequently attempting to contact my outside/Internet IP address which eventually failed as my router doesn’t do forwarding on requests coming from the inside. Not realizing my mistake, I started digging around to actually try and forward the port, until it dawned upon me that the MTA shouldn’t even try to deliver the message through the network in its normal configuration. Sure enough, the test mail that I subsequently sent from outside bounced back in my face with a big “Error 550: relay not permitted” and I recalled recently editing the config files as I hurried to open my text editor.
The bottom line: While melding in updates from the default config file, I had managed to overwrite the line defining the server’s local domains, causing it to omit the ones I had manually added later. I’ve now changed this configuration and moved my local definitions out of the config file (and into the locally imported config that’s provided by my distro for these kind of things), that way, future modifications to the default/global config file shouldn’t affect this setting again.
P.S. I also did a quick scan through the logs and it looks as if I was lucky: the affected domains have a very low traffic volume and apart from spam, no other mail delivery attempts came in while the server was misconfigured. Phew.