Gordon said:
Why would you want to? Outlook by default saves a copy of the sent email in
your Sent Items...
Because that does not prove that your sending mail server actually got your
e-mail or that your sending mail server ever attempted to actually send your
e-mail. All that does is slide a copy of the sent e-mail generated by your
own e-mail client back into another folder inside the same e-mail client.
Some users need proof that the e-mail actually got sent, not that some copy
operation got performed on their own host. For legal reasons, that your
e-mail server accepted your message is not sufficient "performance" (a legal
term meaning that you expended reasonable effort to effect a condition of a
contract) to prove that you sent an e-mail. In a similar vein, you sliding
a letter with postage into your mailbox for your postman to pickup may not
be sufficient legal proof that you sent the letter. You have to send it
with confirmation delivery, registered, or with some other form of tracking
to prove that you actually sent the letter (and you might even get a notary
to validate the content of the letter to prove what was inside and not just
that you sent "some" letter).
Auto-Bcc also affords you some tracking that your mail server ever bothered
to send your e-mail. You don't get that with a copy put in your Sent Items
folder. The only proof (which is indirect) that a copy in the Sent Items
folder provides is that your e-mail client got back an +OK status from the
DATA command that it used in supposedly sending the message to the mail
server.