FIXED: Email Aliases - "Undeliverable Mail Returned to Sender"

I have a few email aliases for my virtual server and some alias servers beneath it. When I try to send email to those email aliases I get an “Undeliverable Mail Returned to Sender” reply. It says:

(expanded from ): unable to look up host localdomain.localdomain: Name or service not known

Any ideas what I’m doing wrong?

localdomain.localdomain is not a host. I think this should read your FQDN instead.
as in the other thread you do have dns problems that need attention.
check your domains at

Ok. I’ve fixed my DNS problems.

How do I set Postfix to read my FQDN for email aliases as you mentioned above?

FIXED: (this worked for my setup…thought I’d share in case it helps anyone else.)

On the Webmin -> Servers -> Postfix Mail Server -> General Options (the first two setting as seen below)

What domain to use in outbound mail Use hostname

What domains to receive mail for Local machine

Since I fixed the DNS issues the error is different now. When I try and send mail to info@domain.tld it goes to the mail queue and sits there with this error: connect to[]: No route to host

I obviously don’t have my FQDN configured in the right place in Postfix(?). Can anyone point me to the right place to configure it. I’ve looked through every config screen on Postfix, but a lot of it I don’t understand.

Thanks ronald! was brilliant! I wouldn’t have know what to do without that link. Thank you.