This is quite nice, really. I’d forgotten the existence of such disposable email addresses.
Why is this not spam?
Besides, IME many services blacklist mailinator, so they probably blacklist a bunch of these others as well.
Of course the world would be a better place if a lot more content was freely available. Having a pdf behind a signup is exactly why these services exist, but this is also the easiest facet of the advertisement war to wage on the provider side.
Just run your own mail server and create disposable addresses or use a catch-all pattern per user (e.g. username-correspondent_name like frank-microsoft or frank-lobste.rs) with a blocklist for abused addresses. I’ve been doing this for decades now, it works fine, I hardly get any spam in my inbox (once per week or less) and I have a simple way of finding messages pertaining to a given correspondent - just search on the `To:’ address.
Yes, postfix makes this ridiculously easy. One setting lets you use any valid character as the separator, the recipient_delimiter option. Gmail uses ‘+’, but a ton of websites reject that either because they never bothered to check the RFCs or because they know about the gmail feature and demand your real address instead. I use ‘.’ on my mail server and it works everywhere.