Yes you can do that.....
Check rewamped script,

echo "START_TIME END_TIME STATUS" >> /tmp/filename_with_error
echo "---------- --------- -----------------------" >> /tmp/filename_with_error

strings error.txt | grep -i "failed" >> /tmp/filename_with_error
if [ ! -s "/tmp/filename_with_error"]
then
echo "No error found."
else
echo "Sending mail."
mailx -r oraadm@juwpkl.gov.my -c adzuan@nc.com.my -s "RMAN Error" adzuan@nc.com.my < /tmp/filename_with_error
fi

# Erasing content of temporary file.
unlink /tmp/filename_with_error

exit 0

Let me know if this doesnt work.

- nilesh