I've seen messages asking Kerio to add some security options to 'groups' since pre-2006. Since it looks like they are never going to work on this issue, here's the work-around I've put in place...hopefully this info will help save someone the trouble of reinventing the wheel.
Unfortunately this method eats a license.
Setup a 'Group' (in my case using Active Directory) with the following settings:
Publish in GAL - unchecked
Setup a 'Mailing List' with the following settings:
Subscription to the list by email - denied
Member can post a message - denied
Non-member can post a message - denied
Moderator can post a message - allowed
Moderators - <Add whoever you want to allow mailing to the group>
Members - All.Employees.Group<_at_>domain.com (created in step 1)
Create a user (in my case AD) with these settings:
Publish in GAL - checked
Forward to address - All.Employees.List<_at_>domain.com
This user can send/receive email to/from his/her own domain only - checked
Now the only address that shows up in your GAL is All.Employees<_at_>domain.com and only the specified moderators are allowed to send to it (others receive error message). No one outside the domain is allowed to send to the address.
In the event someone discovers your group email address (All.Employees.Group<_at_>domain.com) you'll probably have to change the address to something a bit more random since it doesn't have any restrictions built-in.
This is obviously a very kludgy solution, but it seems to do the trick for now. Hopefully Kerio will take the hint and add some of the required options to mail groups and this post will become obsolete.
Hope this info is useful for someone.
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