Email Aliases

I’ve tried to set up an email user as an alias, that forwards email to my real email address.

From webmail, I can send a message from my ‘alias’ to my real email address OK, but if I try to send an email to my ‘alias’ email, I get “Recipient address rejected: User unknown”.

I’ve also tried sending the email to my ‘alias’ using webmail, but it doesn’t arrive at the alias mailbox.

No doubt I’m doing something wrong… can anyone suggest what? Or point me to a URL that explains how to correctly set up an alias please?

Thanks, Max