If the message body contains some text that looks like standard headers eg. From: or Message-ID: then text following these headers is removed when the message is forwarded. These lines are re-written to remove anything that resembles an email address. An email which contains something like the following in the message body: From: A User <email@example.com> is changed when forwarded to: From: A User and the actuall email address part is removed.
*** This bug has been marked as a duplicate of 69723 ***