"+" suffixes are generally a waste of time. Most actors will strip everything between + and @ to avoid exposure like this.

Too many sites disallow the + thing. It's not a great solution.

Sendmail and postfix both allow you to configure that. I have my mail set up so '+', '.', and '_' all work the same. I've never seen any site deny the '.' or '_' character.

If you run your own mail server, you can simply catch-all. The + trick is for the rest.

There are other privacy respecting email providers who give aliases. Posteo and Mailbox.org provide three aliases to begin with. Additional aliases on Posteo are EUR 0.1 per month. Runbox provides 100 aliases per account, and more can be purchased later. Fastmail provides about 600 aliases per account.

Practically, Runbox gives you much more aliases. You can use their own set of domains for each alias which is not small. Can't tell exact number now but around 30 or so. Really handy. There is another problem though. After you've done with many aliases and domains it's getting more and more difficult to maintain. You have to at least vaguely remember which one you have used already. I wish they could introduce a better way of managing aliases.

Is there any technical reason for charging per alias? It’s just an extra $0.00000001 database entry per, no?

It might be to slow alias namespace depletion, and put a cost on potential squatting.

Makes sense on their domain, but if I’m pointing my $1.95/year .info domain at them, I don’t understand the limits.

Fastmail has unlimited aliases, they aren't trivial to set up, but easy enough that I've set up ~10.

That’s not true. Fastmail provides about 600 aliases per account, not unlimited. [1] That’s quite high, but it’s also easy to run out of if one hands out aliases on a per-site basis.

[1]: https://www.fastmail.com/help/account/limits.html

It also supports a catch-all alias though.

Ah! Thanks for the correction.