These are two very handy PowerShell snippets that I use again and again within our work environment.
Retreive List of All Group Members
Add-PSSnapin Microsoft.Exchange.Management.PowerShell.E2010 csvde -f C:\report.csv -s mydomain.co.uk -r "memberof=CN=Dept:MyTartgetGroup,OU=Domain Groups,DC=mydomain,DC=ac,DC=uk" -l "sAMAccountName,name, mail"
Retreive List of All Users with Permission to Email a Group
Add-PSSnapin Microsoft.Exchange.Management.PowerShell.E2010 Get-DistributionGroup "Dept:MyTargetGroup" | Select name,@{Name="AcceptMessagesOnlyFrom";Expression={[string]::join(";",($_.AcceptMessagesOnlyFrom | foreach {$_.Name}))}} | Export-Csv C:\report.csv