Recently, we described how to obtain a list of all mailboxes in the group that has nested distribution groups.
Unfortunately, using this method, you can not get a list of groups in a distribution group, only users (mailboxes).
To obtain this list, you need to write more or less complicated powershell script or use the additive Quest Powershell Module for Active Directory.
After installation of Quest Module, run powershell console and run:
add-PSSnapin quest.activeroles.admanagement
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