Security group email addresses not working.

[springeruk]

I have a problem with security group email addresses, the problem occurs with
all the email clients we use (Outlook 2003, 2007, Entourage 2008 and OWA).

The problem is that email sent to the address does not arrive with the
intended (in fact any) recipients but are also not returned. Further testing
revealed that it is not possible to expand the DL in any of the email clients
all of which return the message similar to the following (this was from
Outlook 2007):

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Cannot perform the requested operation. The command is not valid for this
recipient. There was an error while expanding the list. The list was not
fully expanded
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I also notice when looking at the GAL and selecting Properties there are no
members in this group, but I cannot add them even if accessing email using
the admin account.

I know the group itself is OK as access permissions to certain areas on the
server rely on it.

The only thing I can point to is a complete server disaster a while ago
where we had to recover the entire (OS, data everything) server from backup,
however as everything else is fine that could be a misdirection.

Thanks in advance for any help.