Perform the following steps in the Management Console tree:
To configure the connection to an update source for an unassigned Security Server, maximize the node of the relevant Security Server;
To configure the connection to an update source for Security Servers belonging to a profile, maximize the Profiles node
and inside it maximize the node of the profile for whose Security Servers you want to configure the connection to an update source.
Select the Settings node.
In the workspace, expand the Connection settings group.
If your Internet connection is established through a proxy server, enable the option to Use proxy server.
In the Maximum connection timeout spin box, enter the maximum time (in seconds) that the server will wait for connection to the update source.
The Microsoft Exchange server will be attempting to connect to the update source during this time. The default value of this setting is 60 seconds. You may need to increase it if you have a slow Internet connection, for example.