LINKSYS, HUB, EMAIL PROBLEM

I have a linksys 4 port router and a 16 port linksys 10/100 hub that I have connected to a DSL connection. I have a total of 6 PC’s and 1 of them is connected directly to the Linksys router and the other 5 are connected to the hub. I can see the internet fine thats not a problem. I set 6 email accounts on each PC. The only email account that can send and recieve is the one connected directly to the router. I also opened the ports for SMTP and POP but still the ones on the actual HUB do not work!
Can someone help please?

frank