I think your looking for nat-hairpinning. See: http://wiki.mikrotik.com/wiki/Hairpin_NAT

Inside your "/ip firewall nat" you should be redirecting all tcp traffic destine to port 80 currently to port 8080. You should be able to change that to only match certain src-address-list. /ip firewall address-list add address=192.168.10.0/24 list=PROXY_CLIENTS /ip firewall nat add action...

Hi, I recently purchased a 2011UiAS-2HnD and trying to get more information on offloading services that previously was handled via a linux box. Previously I was running squid and monitoring the access.log. In the event that certain websites or patterns in a url was accessed, and email would be sent....