mHost Map: lookup (domain) deferred

[yapcw]

Hi! I'm getting the above error on sending mails to a domain. i've checked the /var/adm/messages and it showed the below:
" relay=, Stat=deferred"

Previously, sending mails to the same domain gave a different message:
"relay=mail1.domain.com [x.x.x.x], Stat=sent"

This showed that it can't find the relay domain and address now, but i've did a MX record lookup and it returned
the mail exchange domain name but not the internet addr (ip address). Does the failure to lookup for the IP address
cause sendmail to defer the message? how do i configure sendmail to not look for the internet addr or how can
i configure sendmail to send to "this" kind of domains (without internet addr)?

pls advise asap.

thanks in advance!