GW 8 hp 1 server, new install, GW Clients can send mail to other's in domain and outside of domain. The only issue is that GW cilents can not receive email from outside the domain. The failure message is:

<ipaddress of GW server> does not like recipient.
Remote host said: 554 5.7.1 <>: Relay access denied
Giving up on <ipaddress of GW server>.

I can do both forward and reverse look ups.

Seems to be an issue with the server receiving mail messages.