exchange 2003 issues

exchange server delay status Status: 4.4.7 / messages not sent and still in queue
Final-Recipient: rfc822;user@domain.com

Action: delayed

Status: 4.4.7

Will-Retry-Until: Sun, 8 May 2011 19:51:30 +0300

the message still in the queue
and this is only for some domains
other will work fine

i have w2k3 and a cyberoam firewall
what could be the issue
??
how could i troubleshoot this

any help,
many thanks

another issue is
people are receiving our emails on junk/spam folder
what could i do; could i buy some cert or what is needed?? is this ip problem or dns or what

any suggestions plz