[exim] Forwarding question

I'm wondering if there is a way to change the way forwarding is done.
not sure exactly how to explain so here is an example

I have 2 email accounts

john@???
sales@???

john@??? forwards to sales@???

if I send an email to john and sales it goes to both, but when it comes
to sales only as a forward, and I would like it to come as it's own
email. the only way I can get this to happen is to send an email to:
john and bcc sales.

I found this out, because I have a filter in thunderbird, that moves
emails with to: contains john@??? to a folder.

below is something from my logs to show

2013-09-26 12:02:46 1VPExi-0002oZ-Da <= test@??? for
sales@??? john@???
2013-09-26 12:02:46 cwd=/var/spool/exim 3 args: /usr/sbin/exim -Mc
1VPExi-0002oZ-Da
2013-09-26 12:02:47 1VPExi-0002oZ-Da => sales <john@???>
R=virtual_user T=virtual_userdelivery
2013-09-26 12:02:47 1VPExi-0002oZ-Da => john <john@???>
R=virtual_user T=virtual_userdelivery
2013-09-26 12:02:48 1VPExi-0002oZ-Da Completed

notice that the sales one has <john@???> and not <sales@???>
is this because even though the message is sent to both, it knows that
there is the forward so eliminates/trumps the normal email to sales, and
just delivers it like it is a forward?

any thoughts would be helpful

John