configuration Mdaemon with ISA server 2000

i have windows2k server I am using Mdaemon 6 my mail server which is getting mails from ISP POP3 server, it was running perfect but when I install ISA Server 2000 on this computer, mail getting process and browsing on local computer isn’t worked. but its worked ok on client computer.
please solve this problem i m waiting your anserw
thank you