How to send mail from unix

To send mail from UNIX account
At first create ur letter in a file named “letter.txt” using vi.
And then
$ mailx –t rakib004@yahoo.com < letter.txt
or create at once and to send it..

$cat letter.txt |mail –t rakib004@yahoo.com
Or
$echo “Hey sorry Pal...I cant put emoticons... “ | mail –t rakib004@yahoo.com

Full Format:(-s means SUBJECT,-c means TO,-b means BCC)
$cat letter.txt |mail –s "HI" -c rakib004@yahoo.com -b ma_hasim@excite.com

I want to get my name as sender? How to do?
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Use sendmail instead of mail or mailx.
Format:
$cat letter.txt|sendmail -F "yours mail id" "receipient`s mail id"