i am trying to execute the below script for sending mails from unix

MAIL1="xyz@yahoo.com"
mailx -s "hi" $MAIL1<message.txt
if [ $? -ne 0 ]
then
echo "failure"
else
echo "success"
fi

but iam unable to send this eventhough iam getting success in the output

if i logout and login i have a "you have new mail"
if i type
mail in the $ prompt then that pariticular mail is not deliver but it delivered to local user?
should i do any configuration before sending mail? please help me this is urbent:-(

Check your messages file for errors - if you don't know where (or if) mail errors are logged, check /etc/syslog.conf.

Check that DNS can find the IP for yahoo.com mailservers -
$ nslookup
> set type=mx
> yahoo.com

If your DNS isn't finding a mail exchange record then your system is simply bouncing the email back to the local user due to that error.

You can also check sendmail with the following:
$ /usr/lib/sendmail -d0.1 -bt < /dev/null
which will output info on what sendmail sees as far as configuration. Check that it's using DNS (look for NAMED_BIND) and check that the system identity comes out with no issues.