Getting a "Deferred: 451 4.3.5 Server configuration error" while running mailx
 

Hello All,

I am trying to test mailx command on one of our RHEL 5.4 servers. Based on some guidelines given by our systems guys....I did the following step 1-6

1. Log in to the Linux host as root where you want to configure mail relay
2. Edit the /etc/mail/submit.cf and search for the word "DS".
3. Append the Mail Relay server name after the word DS. # "Smart" relay host (may be null)
DS<mail server name> I added this correctly
4. Stop the sendmail.
/etc/init.d/sendmail stop
5.Stop the sendmail from starting when the host boots next time.
chkconfig sendmail off
chkconfig --list sendmail
6.Test email.
mailx -s "test at `date`" -v "my e-mail id" < /dev/null

I was able to configure this correctly on one of the RHEL server, but on a second RHEL server, when I try the mailx command, I get the following output.

Null message body; hope that's ok
a@b.com... Connecting to a.portal.b.c. via relay...
220 a.portal.b.c ESMTP
>>> EHLO server.host.name
250-a.portal.b.c
250-PIPELINING
250-SIZE 10240000
250-ETRN
250-STARTTLS
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
>>> STARTTLS
220 2.0.0 Ready to start TLS
>>> EHLO server.host.name
250-a.portal.b.c
250-PIPELINING
250-SIZE 10240000
250-ETRN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
>>> MAIL From:<root@server.host.name> SIZE=69
250 2.1.0 Ok
>>> RCPT To:<a@b.com>
>>> DATA
451 4.3.5 Server configuration error
a@b.com... Deferred: 451 4.3.5 Server configuration error
554 5.5.1 Error: no valid recipients
>>> RSET
250 2.0.0 Ok
Closing connection to a.portal.b.c.
>>> QUIT
221 2.0.0 Bye
[root@server.host.name ~]# ping a.portal.b.c
PING a.portal.b.c (xx.xx.xx.xx) 56(84) bytes of data.
64 bytes from yy.yy.yy.yy: icmp_seq=1 ttl=63 time=0.296 ms
64 bytes from yy.yy.yy.yy: icmp_seq=2 ttl=63 time=0.303 ms
64 bytes from yy.yy.yy.yy: icmp_seq=3 ttl=63 time=0.322 ms
64 bytes from yy.yy.yy.yy: icmp_seq=4 ttl=63 time=0.389 ms

--- a.portal.b.c ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3000ms
rtt min/avg/max/mdev = 0.296/0.327/0.389/0.040 ms

I am sure I enetred the right recipient address and tried it 2-3 times with other e-mail recipients too. Also, the same e-mail recipient and mailx command works from another RHEL host.

Any guidance/pointers is truly appreciated.
Thanks