Log on to Forefront TMG 2010 server using admin credential. Open Forefront TMG Management from start menu. Expand Forefront TMG>Firewall Policy>Select Tasks>Click Publish Exchange web client access.
Click New button to add Exchange Farm i.e. Exchange CAS servers you have installed.
Click yes to accept changes you made.
In this step you will be adding Exchange web listener or CAS servers.
Select an web server certificate you have installed before hand.
Important! You have to install web server certificate before you proceed adding publishing rule.
Publishing Mail Server
Expand Forefront TMG>Select Firewall Policy>Select Tasks>Click Publish Mail Servers
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