problem with virtual users on postfix 2.1.5 on fc3

[Ankush Grover]

hey friends,

I am running postfix 2.1.5 on FC3. I have entered all the virtual
users for my domain in virtual file and I have configured postfix with
these settings in main.cf

virtual_alias_maps = hash:/etc/postfix/virtual
virtual_alias_domains= testing.com

The problem is that few of my users does not use this mail server they
directly download the mails from the ISP like marketing people, the
directors. So I had made the entry like this in virtual file

user1 at testing.com             user1 at testing.com
marketing at testing.com       tom at testing.com  --> mails for marketing
should go to the user

  tom mailbox

means if the mail is send by any user from the Internal Mail Server
for the user1 the mail should to go the ISP mail server so that the
user1 can get this mail.

Now the problem is that if somebody sends the mail from ther Internal
Mail Server which is running on postfix this mail gets bounced with
the following error

  2 16:57:46 test1 postfix/smtpd[11206]: NOQUEUE: reject: RCPT from
test1.sun.net[192.168.1.125]: 550 <user1 at testing.com>: Recipient
address rejected: User unknown in virtual alias table;
from=<ankush at testing.com> to=<user1 at testing.com> proto=ESMTP
helo=<test1.sun.net>

If I take out this virtual_alias_domains= testing.com then postfix
accepts mails for any user for my domain which I don't want to do .

How to get rid of this problem ?

Thanks & Regards

Ankush Grover