Groups cannot be nested more than <number> levels deep

What happened

You sent mail to a user group containing the name of another user group, a feature called nesting. The address in your active mail message exceeded the number of levels of nesting that IBM® Notes® allows.

What you can do

To solve the immediate problem, specify the individual users to whom you want to send the message, rather than the group names.

As a long-term solution, ask your Domino® administrator to consolidate your user group names in the Domino® Directory.