Users can add them to Distribution Groups

Hi

I have a smaller problem at a customer. It seems that ordinary Domain Users can add them self to Distribution Groups they have no permissions on. In fact they can manage the groups.

I can not find the cause.

In Exchange 2010 EMC the group has one manager, and it is a closed group.

I have made a test with a new testuser which is only in the Domain Users.

Have someone seen this before?

It is old groups back from 2003. If I delete one of them and create it again via 2010 EMC everything seems fine.

Br
Steen