[hamburglar]

Edit: oh god, leaving this in place for posterity but I am completely misrepresenting fastmail here. It is protonmail that I recently tried and had these limitations. Apologies! How embarrassing. Also, I have no idea why the child comment correcting me would be so downvoted. It’s apparently correct.

Yes, but fastmail has a couple dealbreaker limitations when doing this: First, you can’t originate mail from that address; you can only respond. This makes it unusable for a lot of mailing list control messages and other systems where you are required to make inquiries from a registered email address. Second, you must explicitly set up each of the unique recipient addresses, which is a huge burden when you want to be able to generate them on the fly when signing up for web accounts (and when you already have hundreds in use because you’ve spent decades giving every company a unique address).

If they addressed these and I could have an unlimited number of suffixes directed to a single fastmail address, I’d sign up for a paid account in a heartbeat. Looks like a great service but those are fatal flaws IMO.

[duffmancd]

This doesn't match with my experience. I have a single catchall *@my-domain.com address that will receive anything sent to the domain (without setting up separate accounts ahead of time).

You can also send from any address, but I agree that the UI is a bit hidden. You first choose from the from-address dropdown "*@my-domain.com", and then a new textbox appears where you can type what address to send from. As another commenter pointed out, if you are replying to an email it will automatically fill in the custom from-address, but you can overrule it.

[cstrat]

You can originate emails from anything - it just requires that you set it up as an alias (and you can set custom signature etc...)

You don't need to explicitly setup recipient addresses! I can have as many [e-mail] addresses, where xxx is anything at all. [e-mail] is my main email address.