Normally, the buyer would see the message as "From:" whatever Display Name and Display Email that you have entered in E-junkie Seller Admin > Edit Profile.
However, since the message is not actually being sent from a mail server @ your domain, the anti-spam policies of major email providers require that we identify ourselves, the real sender, by adding an extra header, "Sender: client@e-junkie.com". Omitting that extra header would greatly increase the likelihood of our thank-you emails being flagged as spam, so retaining it is really in the best interest of buyers and sellers alike.
Normally, that extra Sender: header is not shown at all in most email programs, but the Outlook email program is a bit quirky in the way it displays such messages, as it combines the From: and Sender: headers of the original message and displays them together as "From: [Sender: address] on behalf of [From: address/name]" (unfortunately, there is no way to avoid or work around Outlook's behavior in that regard).
