How to forward (all) domain email (no account created)

[sleuth1]

tricky one client asked me to forward a domain to a cname web hosting designer company very weird , so used the domain forwarder in WHM , works fine

But the said company does not want to host email for the domain, the trick is you cannot create just a mail server for any account ,in fact cant create any sort of account for this domain without messing up the web forwarding need something like *@.domainname.com to forward to mail.domain.com , has anyone done this?