Bulk update of distribution group security.

Hi,

I am trying to update all of our distribution groups to only accept mail from authentication users I am trying to use powershell to do this as we have over 500 off them.

I have tried the command below but it says the command completed successfully but that no attributes on the distirbution groups was moddified.

Get-DistributionGroup | Set-DistributionGroup -RequireSenderAuthenticationEnabled $False

Any help would be greatly appreciated.

Thanks