mime contents thru ipfw

[Hugo Osorio]

Hello, 

I need to change some settings on the firewall to forward html mime contents 
packets to the proxy and back, please how can i do that.. 
the LAN on which i am is unabled to make any attachments.. and i can not 
sometimes to access gmail, i suppose this is the reason.. but I need 
guidance, in order to know where, and what to set in my firewall file, 

thank you very much, in advance