cannot send mail
 

I'm new in Linux (Red Hat 9). We setup this to be our Internet/Mail server in our network. The Internet is working fine but the email cannot send out messages. It can receive messages. The error display is this

*****
An error occured while sending mail.
The mail server responded:
5.7.1 <email addrs>...Relaying denied. IP name lookup failed [ip addrd]
Please check the message recipients and try again.
*****

The email address is valid. Any solutions on this. Need help.

Get an MX record ... these hardly anyone accepts e-Mails
from machines without a reverse lookup entry.

The "problem" is most likely not with the machine but
with the way you're hooked up to the internet, I assume
you're using some ISP account and haven't got a
registered server?



Cheers,
Tink

Before we install it I got the MX record you referring. We also inform the ISP company about the shift to Linux.
What do you mean "the way you're hooked up to the internet"?