exchange server

hi all
I realy need your help i was having a problem with my exhange server that i coudnt get any outside mail and iv just changed my exchange server to a newer one. still i was geting the same prob i later on find out that my prob was that i had the DHCP server service enable on my router so my DHCP service on my exchange server coudnt start at all.so i got the service on the router disable by my lan provider.so now the DHCP service on my exchange server now start normaly and im able the recive and send mail but im not able to send and recive mail from gmail and hotmail client at all and i dont have any client blacklisted.so any idea what causing this problem?
tanx