How to create single email for each service I use?

Most custom email domain hosts should have an option to allow you to catch all emails *@example.com (e.g. Protonmail has this option for paid plans [1])

I have heard some people say this attracts a lot of spam since you'll receive emails from any and all usernames@example.com. You'll probably need to create custom email filters and whitelist emails that you want to receive and trash the rest.

[1] https://protonmail.com/support/knowledge-base/catch-all/

Wife and I have been doing this for the last 10 years or so (using catchalls) and I can share a few thoughts based on experience: (1) We try to use addresses that will immediately identify the sender (e.g. homedepot@xxxxxxx.com). This has the added benefit of allowing us to see which companies might be selling our information to other entities (or which have potentially had data breaches). We've also been able to identify when employees leave a vendor we use and take the mailing list with them. For example, I had several of my clients with a large hosting/colo company and created unique account emails for each, e.g. client1.hostingcompany@xxxxxxx.com, client2.hostingcompany@xxxxxxx.com, etc.). When my sales contact left the hosting/colo company and joined another unrelated (CRM software) company, whaddya know... each of these truly unique email addresses which had never been used anywhere else suddenly started receiving unsolicited email from the CRM company. (2) Spam can be an issue when you use catchalls for several years. Once one of your custom-defined emails finds it way onto a single list, it will suddenly start receiving emails from MANY spammers as the list propagates. This is manageable with filters, but be aware that it carries a bit of time/labor cost. (3) It is sometimes quite fun (and potentially useful) when a big company asks for your email address on the phone. Let's say I am talking to a Seagate support person and they ask for my email address. I tell them 'seagate@xxxxxxx.com' and there's usually a brief pause as they struggle to understand. Sometimes it's a bit funny, other times I notice an immediate positive change in their attitude (almost as if they think I am part of some quality control or secret shopper team) YMMV.

Others covered the account+servicename method. FastMail also supports account@servicename.mydomain.com: https://www.fastmail.com/help/receive/addressing.html

FastMail webmail also supports sending and replying from that address (or any other on your domain) without explicitly configuring the address.

The + addressing scheme is well known, and more talented spammers will easily avoid it.

The problem of the catch all address has already been discussed.

What I want to see is a crypto hash of the domain (with a salt) and use a part of that as the e-mail address. And I want to automate the creation AMD use of that address in my MUA. So, when I respond to one of those messages, the MUA makes sure to use the right hash-based address as the sender.

Create a domain on gandi.net (or possibly some other provider, been a gandi customer over a decade so that's what I know) create an email on your new domain. Then whenever you need an email for a service create an email alias and point it to your "real" email. This is precisely what I do.

They have an API, you could also automate this, I intend to create a script to create the alias but just have never gotten around to it.

You can use SimpleLogin [1]. It's available as a web app, Chrome/Firefox extension or iOS/Android app.

[1] https://simplelogin.io

https://tools.ietf.org/html/rfc5233