Already in the past I've been (ab)using Fastmail's email alias feature for this kind of purpose. Though it was a bit inconvenient as the UI always said that it takes 15 minutes for the new alias to become fully active. Great to see they now have simplified this!

I'm a current user of Fastmail and set up a wildcard alias for this purpose:

https://www.fastmail.help/hc/en-us/articles/1500000277942-Ca...

When I get spam to a particular alias, I blacklist it to my spam folder. Naturally this might get a little difficult if a spam bot ever figures this out where I'd need to move to a whitelist rather than blacklist process. But it's worked flawlessly for years so far.

At least with my method I don't need to create the alias in advance.

This is good to know. I might use this in a few scenarios, but I would not be willing to implement a password management service to get it.