From the General Administration page, click the News Server server name button > Expiration > View/Manage Expiration Policies.
Under Custom Expiration Policies, click Edit under the policy you want to modify.
In the Custom Expiration Policy form, click the For drop-down list > select the discussion group criteria for which you want to specify the expiration policy.
In the Discussion Groups Matching field, type the discussion group name or pattern that you want to create the policy for.
To determine how long you want to keep the articles from the specified discussion group on disk, select one of the following options:
Do not specify this option if you want to maintain control over the expiration policy of all articles stored in your spool.
Click OK.