I use a different email alias for every single company that all forward to my single email account. Services that I recommend are Addy.io or SimpleLogin

I use Proton, and they own SimpleLogin, which generates email aliases.

SimpleLogin email aliases point to your email address, and if you respond to any emails sent through simplelogin, it replaces the "from" field on your outgoing email with the address you used as an alias.

The simplelogin browser plugin tags all of your aliases with the domain of the site you're currently on(so if you go go lemmy.world and click on the "sign up" link, once you're on the sign up page, you click the simplelogin browser extension, and it will generate an alias to use for signing up for lemmy.world and will tag it "for lemmy.world", so you know where you used that alias). So the moment you start getting spam to any simplelogin email alias, you just go and disable the alias, and you know EXACTLY who gave your email address to a spammer.

I use my own domains, so I create alias addresses as I need them and I can just as easily delete them.

I have my email client sort incoming stuff into folders by those addresses to keep all shopping spam separate from my actual communication.

DuckDuckGo offers a free email aliasing service through their mobile app (available on F-Droid).

Proton.me is free and privacy respecting, and they have aliases, but inbox size is relatively small on the free tier.

You could also use duckduckgo aliases with any email provider

I think Port87 may be what you are looking for.

"Sharing a different address with every app or service keeps them from tracking you. If a company leaks your email, you can easily change a label’s address and block the address that was leaked, preventing spammers from reaching you."

I don't think there are any trackers or data collection. The developer/owner of the company is on the threadiverse (@hperrin@lemmy.ca) and their is a !port87@lemmy.ca community. Perhaps they can confirm. @hperrin@lemmy.ca?

It has a free tier, but that tier only allows you to receive email, not send. Cheapest sending email account is $0.99/month.

You said you don't care about the country, but for completeness, their contact info has a San Marcos, CA, USA address.

I use it and really like the "sub-emails" I can make for each type of email or per company.

Your first and last points are indeed mostly incompatible. Tuta (free) is an option, however they have been known to close free accounts for being unused. Mailbox.org is what I'd recommend, it's very cheap (a few dollars a year if I recall correctly) and allows for catch-all inboxes if you have your own domain. That means you can have emails like "shoeshop@yourdomain.com".

Alternatively to the domain, you could pay for something like simplelogin, which allows you to create and manage unique email addresses which forward to your actual email if enabled. It's how I determined the source of a past data breach before it was even publicly announced.

Personally, and perhaps oddly, I have a paid Tuta account with simplelogin forwarding to it, and then I also have a mailbox.org account which simplelogin also forwards certain emails to. That's because Tuta requires you to use their own client, and they do not have api level access (that I know of), so my package tracking automations have to use mailbox.org via imap instead.

Fastmail, it’s such a solid service. It is paid, because if it were free it would violate ask #1 from you

You’re not going to find free + no data harvesting

Tuta and Addy.io. I paid for both with Monero.

If you have a spare domain or something, you can use faivelo, you'd get with them unlimited mailboxes and aliases so you could make a mailbox or alias for each provider you signed up with, and that way keep track like if you saw the netflix@yourdomain.com email pop up somewhere you would know whos been snitching

It’s not free, but it’s easily worth it IMO. Get a domain such as FUcorpoTrash.wtf or whatever you consider fitting. Get Tuta mail, and set it to use a catch all email in that address. When you need to sign up with some Sketchy Store, you just make a new sorting rule for them. Everything they send to sketchy_store@FUcorpoTrash.wtf gets automatically sorted into the appropriate folder in your Tuta mail. I would recommend making a new address for every site. Takes a while to set up, but you’ll be able to control your email just the way you want.

Mail service has become so important nowadays, it makes sense to think about paying a couple of bucks for it. I use mailbox.org for many years now, and it is excellent. It I buy stuff I just create a new alias like localhorst-shop24@mailbox.org. They also have the option to create temp mails.

There are some other features I like and use frequently, my Calendar I connect via CalDav, a free video conference tool, a file storage I can use to share files with third party (think of nextcloud light).

Posteo. For me, a big part de-googling, was also ensuring that the amount of emails that I get is reduced.