2 1/2 months ago we had a new AD/exchange 2010 server 2008 enterprise r2 infrastructure
all our users/mailboxes were migrated across using Quest.
we have a group containing all users in the company that we restrict who can send to it. in the old domain, it was a security group that was mail-enabled. now its a Mail Universal Security Group. ever since the migration, we have been unable to add users under the properties of the group>Mail Flow Settings>Message Delivery Restrictions>Message Delivery Restrictions>Only senders in the following list.
every time a new user is added and we "ok" out of it, we get an error saying "members can't remove themselves from security groups. please set the group to closed for requests to leave." (image attached)
of course, i'm not trying to remove anyone, but i assume the error is pointing more at the fact its a Mail Universal Security Group.