In comp.os.linux.admin Fai <faiyazm@mspli.com> wrote:
> We are using redhat linux 9. We have configured sendmail. We are able
> to send mails but not receiving them. When we cheked the log we came
> to know that there is an error "unknown host", "My unqualified host
> name (mailserver) unknown; sleeping for retry". Log file has been

Give yourself a correct hostname, with a domain part. And list it in
/etc/hosts.

> pasted in this message. We are not finding where we r doing wrong.

You are not looking at the message. It says (1) the hostname is
without a domain part, (2) it can't resolve your hostname to an IP
address anyway.

You fix (1) by giving it a hostname with a domain part or by letting
the "hostname" be an alias for a FQDN resolved through, say, /etc/hosts.
Anyway, you have to fix (2) the resolution issue, so you might as well
edit /etc/hosts.

> Please give us a solution.

Hire somebody (more) competent.

Peter