fastmail.com allows it. I'm apparently paying "legacy account" rates, which probably highly tempers my recommendation. I pay something like $5 or $12 a year for service. 500mb mailbox. I don't use calendar or anything else so i have no idea if those are restricted.
I'm on the $95/2 year plan, with about 30GB stoage, and have several domains attached, all set up for catchalls.
Trying to explain to a business why their name is in the email address you just filled out on a form is fun sometimes, though, but the only complete rejection I've gotten for it though is the guy who runs the main groups.io for one of my amateur radio transceivers and can't wrap his head around my address not being some attempt at fraud.
On rare occasion I’ve encountered companies (let’s say foo.com) that prohibit the string “foo.com” from being in the email address I sign up with — some slightly broken defense against preclaim or impersonation attacks I guess?
I've just started using random triples/quartets of letters at my domain. There's pretty slim advantageein literally getting email from bestbuy@mydomain.net.
I pay €1/month for Tutanota which lets me have five aliases, however using DNS redirection with my domain I can have a unique receive address per website.