I fixed the problem by allowing port 161\162 for incoming traffic on the SupportAssist server. Thanks.
Setting up my first SupportAssist Enterprise server. Everything works as expect except the snmp configuration on iDRAC. When I added a new iDRAC to the server, it always complained that it is unable to verify SNMP configuration. The only workaround is I turned off the local Windows firewall where the SupportAssist server is installed. I checked the SNMP traps and Email settings on the iDRAC and did see that the alert destination address has the SupportAssist server IP configured. So the SNMP configuration is working. So what local firewall rule should I create to address the above issue? Thanks  
snmp configuration problem