How to accept mail with unregistered mailbox names ([email protected]) on shared hosting?

Question

Mail server

When registering on a third-party site othersite.com, users enter their_mobile_number @ mysite.com . And because your_mobile_number is not predictable, mysite.com server returns 550 error (user not registered).
How to make the mysite.com server accept mail for non-existent mailboxes?

Answer 1

More or less like this

Answer 2

I actively use this with Yandex mail - my personal site is on a regular shared
------------------------------- -------------------------------------------------- ----------