Re: A subscription fee for email‽
"All" emails at my domain exist - I don't have to create accounts/aliases.
It doesn't mean that they will go anywhere useful until I authorise them to, however. They get held in limbo/quarantine until I allow that alias to deliver mail onwards to the real inbox.
Catch-all on the domain, mailbox storage on the catch-all, forwarding only for listed aliases.
I literally do <companyname/code/made-up-on-the-fly-names>@mydomain.com and email always gets delivered (I have a 5-minute greylisting on new aliases, so obvious-made-up spam rarely delivers even into the holding mailbox).
The worst I ever have to do is override the greylisting if I'm bored of waiting the 5 minutes that they are asked to wait before retrying delivery.