Today I had the need to add a single user to all the Distribution Groups (around 120) within my Exchange Environment. Thankfully doing this task via Powershell this is a very simple "one liner".
All you need to do is open an Exchange Management Shell Window and Type in the following command:
Get-DistributionGroup | Add-DistributionGroupMember -member Administrator -ErrorAction SilentlyContinue
This command will in essence get every distribution group that you have setup within your environment Get-DistributionGroup and then using the Add-DistributionGroupMember command add the selected user (in my example “Administrator”) to each group. I have used the -ErrorAction SilentlyContinue Switch to allow the command to continue, should the account be determined to already be a member of any of the groups.
Just as a point of note – if you are using Exchange 2010 and have configured moderation with RBAC on your Distribution Groups, you should modify the command to look like the following:
Get-DistributionGroup | Add-DistributionGroupMember -member Administrator -BypassSecurityGroupManagerCheck -ErrorAction SilentlyContinue
The added parameter -BypassSecurityGroupManagerCheck allows for admins whom are not specifically owners of the Distribution List to modify the group membership (more about this can be read here: http://technet.microsoft.com/en-us/library/bb124340.aspx)