[Dovecot] test emails did not arrive at SMTP server : after dovecot installation

[sunhux G]

Just set up postfix & it's running on my RHES 4.2 box.

Immediately after postfix is up, I test sending emails from a permitted
domain
(ahhh, on this postfix server's domain firewall, we even have a firewall
rule
 which permits Tcp25 from those few sending domains' SMTP servers) using
an email client  to sender_id@[IP_address_of_the_postfix_server]  & the
/var/log/maillog on the postfix server indicated the email arrives at the
postfix
server (with some errors though) :

# grep recipient_id /var/log/maillog*
maillog:Feb 15 11:41:52 hostname postfix/smtpd[6891]: NOQUEUE: reject: RCPT
from gate1.mds.com.sg[203.126.130.157]: 554 5.7.1
<recipient_id@[202.6.163.31]>:
Relay access denied; from=<prvs=020cae8c4=recipient_id at mds.com.sg>
to=<recipient_id@[202.6.163.31]> proto=ESMTP helo=<gate1.mds.com.sg>
maillog:Feb 15 13:43:20 hostname sendmail[7688]: NOQUEUE:
SYSERR(recipient_id): can not chdir(/var/spool/mqueue/): Permission denied

Then I installed dovecot rpm on my RHES box : uninstall it as it's an old
version &
reinstall with a newer version & start up dovecot as well.

I did not test sending to sender_id at domain_name at that time because the
domain I purchased from a domain provider/registrar has yet to be registered
in our ISP's DNS.  Subsequently I registered the following A, MX & NS
 records with our ISP :

A: myportaltech.com. IN A 202.6.163.31
A: smtp.myportaltech.com. IN A 202.6.163.31

PTR: 31.163.6.202.in-addr.arpa. IN PTR smtp.myportaltech.com.

MX: myportaltech.com. IN MX 10 smtp.myportaltech.com.

NS: myportaltech.com.        IN     NS     ns1.businessexprezz.com.
NS: myportaltech.com.        IN     NS     ns2.businessexprezz.com.

The above myportaltech is just a fictitious name of my domain but I
can provide the actual domain name if needed.

After the above records have been propagated to all other DNSes, I
test sending email from the same permitted domain, this time using
domain name & the email never arrives & I did not receive a 'bounced
mail' notification too.  Then I test sending from the same domain to
recipient_id@[202.6.163.31] & this time round, the test email never
show up in /var/log/maillog* anymore.

The network/security guys confirmed that the firewall logs did not
show any denied SMTP records.

So how do I go about troubleshooting this?

Is this a DNS record entries issue, firewall/network issue, related to
dovecot or something within my postfix server?


Thanks
Sun