The Send drop down menu is used to request physical movement of your mail, either by shipping or picking it up, transferring it to another user on the account or returning it to Earth Class Mail for resolution.
You may ship mail to any location you choose using the Shipping interface. For more information please visit Creating Shipments.
If you would like to transfer a mail item to another user on your account, select the Transfer option. For more information please visit Transferring Mail.
If you have received a piece of mail that is not yours, select the Not My Mail option. For more information please visit Returning Mail to ECM.