Yes, exactly like that.

I’ve had companies just not respect your opt-out preferences. I’ve seen regularly they add new email categories (presumably maliciously) so that they can continue spamming you.

Less commonly they will sell your contact info to third parties

With an email alias you can simply disable that address, and any emails sent to it will be bounced back to the sender.

Also keep in mind that email is one of your main personal identifiers (PID) on the web. When data mining companies buy up information from various sites and services, they use it to link together your activity in order to expand your profile.

With self hosted email and at least Proton Mail (and probably other paid solutions), you can set up a “catch all” address. With that, any non existing email gets redirected to one; for me, I have spam@domain.com so, while myname@domain.com goes to my inbox, thisaddressisinvalid@domain.com and, I don’t know, walmart@domain.com both go to spam@domain.com. I don’t need an individual entry for every alias and I can specifically block any address that’s particularly spammy or compromised.

I hear that you can have a similar setup with something called SimpleLogin, but I’ve never tried that.

Yes indeed, password managers have the option to do this, at least Protonpass and Bitwarden. While Bitwarden you need to connect a third party email service. But it’s relatively easy, especially with Protonpass as it will automatically suggest to do this when you create an account somewhere.

Back when I used self hosted mail, I wrote an extension that requested a new alias based on the domain of the website.

Like website.net_d5g4j8@mydomain.com

If the site got compromised I would update the random characters.

I still have 800+ aliases left over from this. But after moving to hosted mail I never updated the extension.