You now need to subscribe the mail alias to the mailing list. Check with the mailing list information as to how to subscribe. Some mailing lists allow you to subscribe an email address that is different from the address from which the subscription comes (they check back to the address to be subscribed for confirmation before actually subscribing that address).
Other mailing lists do not permit this. So you may need to 'forge' a subscription request. There are many ways of doing this. One of the easiest is to use Netscape mail set up (temporarily) with the address to which the mailing list is to send the mail.
After subscribing, you should see a 'welcome' message of some kind from the list server in the news group - in which case all is well and you can now test the other direction by posting a news message to your new list.
The message should *NOT* appear in the newsgroup at once. It should get sent out by mail and then received back and posted to the news group.
If this works, you have succeed in getting the list gated to news.