[exim] migrating exim/spamd/clamav server

Hi all,
I am migrating an exim mail sevrer on to new hardware latest app versions.
For testing I need to send a copy of all in-coming emails to the new built
server, do the content scanning, and suppress its delivery.
Would you know what router should I use to achive that, without disrupting
the live server at all?

thanks

Dimitri Koutsos