Mail with From Address

hello all

When i send an email using "mail" command, it is received by intended receiver but From Adress is getting displayed as user@hostname.
Is there any way to change the From address of Email to xxx@bbb.com?

Apprecite your response

echo "testing 1 2 3 " | mailx -s "subject" -r <sender_mailid> <receiver_mailid>

 
(
echo "From: xxx@bbb.com "
echo "To: xxx@bbb.com "
echo "MIME-Version: 1.0"
echo "Content-Type: multipart/alternative; " 
echo "Subject: Test HTML e-mail." 
echo "Content-Type: text/html" 
echo "" 
echo "Test Email"
) | sendmail -t