we have an hmailserver in the local network with local domain, n.3 pop3 account for receive and storage mail, n.3 smtp account for send out mail.
the issue is that with a local domain we can't send out mail because HMAILSERVER from is "localaddres" and with local domain the mail out message is : 501 invalid domain.
with gmail route no problem and work fine!
with other provider we have the issue.
we search a workaround to solve this issue and can send out mail with rule / script or other.