Hi Peter,

> We're running Forefront for Exchange 2007 and trying to send a large .ZIP
> attachment it's being blocked with the message "Large uncompressed size"
>
> Is there anywhere to set what size this triggers at?

You might want to check this:
http://support.microsoft.com/kb/924952/en-us

Regards,
Dieter

--
Dieter Rauscher
MVP ISA Server
Website: http://www.msisafaq.de
Blog: http://msmvps.com/rauscher/
Buch: http://www.msisafaq.de/buch/