More 'ops' than 'programming', but: Email. Email is a real 'devil in the details' thing. Anyone can follow a web how-to (when they're not stale) and set up a b

More 'ops' than 'programming', but: Email. Email is a real 'devil in the details' thing. Anyone can follow a web how-to (when they're not stale) and set up a basic server, but it's crazy complex to understand properly. It's also weirdly both old-as-rocks and at the same time constantly changing (eg: deliverability scores, major vendors changing how they accept things, etc). Aliasing and mail flow and MUAs vs MTAs and mailbox formats and multiple arcane config files and blacklisting and DKIM and MX records (and TXT records) and etc etc etc... and if you're really crazy, GPG-signing. I've always got enough to just scrape by, but never actually comfortably grokked it all at any point. So many disparate spinning plates...