zip file has problem with 'Attempt to hide real filename extension' error

[Charlie]

Hi,
I have created a blank file called mispb-misyahoogroups.com.out
I am able to send this through my mailserver with no problems. However, when 
I zip up this file, and call it mispb-misyahoogroups.com.zip Mailscanner 
objects to this, with the following error:
Quarantine:
    Report: Attempt to hide real filename extension 
(mispb-misyahoogroups.com.out)
    Report: Attempt to hide real filename extension 
(mispb-misyahoogroups.com.out)

I have commented out the line in Mailscanner as per the following, and 
restarted Mailscanner.
#deny   \.[a-z][a-z0-9]{2,3}\s*\.[a-z0-9]{3}$   Found possible filename 
hiding                  Attempt to hide real filename extension

I am now at a loss as to why this happening,

Thanks very much
Charlie