I've sent for your replacement.
I sent my friend an Email.
The bearings where sent north
Please take the forms sent with this letter.
By default, the copy of the message will be stored in your Sent Messages folder
"sent." is an abbreviation that you could use.
The detective was sent to investigate the dark room.
She added an emoticon, then sent the email.
"I sent you to the principal because you misbehaved."
The story was sent for the contest. (maybe it would be better to use 'sent in'). The story was sent in for the contest.
Yes, it is correct. You are correct to use "who" and not "whom" because "who" is the subject of the clause "who has sent him."
I sent a missive to my mother while I remembered to do so.
His eyes were downcast as he was sent to his room with no supper.