Backing up Distribution group permissions and removing mail enabled security group restriction

Hello Everyone,

Can any one help me to to sort out the issue of how to take a back up of existing permissions on exchange distribution groups and remove one user from existing permissions added by using the below command

set-distributionGroup -AcceptMessagesonlyfromSendersorMembers cmdlet

there might be 3 groups allowed to send to this group but i want to remove only 3rd not all.

one way to take a backup is to run command get-distributiongroup "distributiongroupname" | fl Name,AcceptMessagesonlyfrom > c:\backup.txt but restoring will be a tiedious task when there are more than 5000 distribution groups.

Or is there any way to undo the set-distributiongroup command previously run

Thank You,

MYM