Maybe I am mis-understanding what you are seeing.
When I forward a message, the receiver will see the original mail (unless I edit it, such as removing any previous sender's information) and the length will be the same as the message was before forwarding except for the added line "Begin forwarded message" (again, unless I edit bits out), and there will be no attached copy of the original message.
So when you say in your reply above "The orginal email with the sender's name and address was also sent with my forwarded email." do you mean:
a) that it is still visible at the head of the text of the message (which I was saying does not happen for me because "after hitting delete, the previous sender's information disappears." [and since] "it has disappeared, it cannot be in your forwarded mail." Disappeared means it is not there.
b) another copy of the original message is attached to the forwarded email at the end, either as an included file or as repeated text.
c) some other situation.
Sorry about the previous mis-spellings! I hope that we can get to the bottom of this.