reject_unknown_client with pop-before-smtp

Hi,

I have a running Postfix with pop-before-smtp needed for authorising
several clients, which use laptops with mobile connection (their IP
addresses deffer each time they connect to the web).

I want to apply 'reject_unknown_client' in 'smtp_client_restrictions'
and 'reject_invalid_hostname' in 'smtpd_helo_restrictions' but this
rejects my mobile users as their IP's are not correctly resolved. Is
there a way to tell postfix that the IP's in the pop-before-smtp's db
are part of mynetworks and if there is, how is this done?

Curruntly my configuration is:
mynetworks_style = subnet
and my local network IP's are 192.168.10.*

Thanks