Get-DistributionGroupMembers.ps1

################################################################################################################################################################
# Script accepts 2 parameters from the command line
#
# Office365Username - Optional - Administrator login ID for the tenant we are querying
# Office365Password - Optional - Administrator login password for the tenant we are querying
#
#
# To run the script
#
# .\Get-DistributionGroupMembers.ps1 [-Office365Username admin@xxxxxx.onmicrosoft.com] [-Office365Password Password123]
#
#
################################################################################################################################################################ 

#Accept input parameters
Param(
    [Parameter(Position=0, Mandatory=$false, ValueFromPipeline=$true)]
    [string] $Office365Username,
    [Parameter(Position=1, Mandatory=$false, ValueFromPipeline=$true)]
    [string] $Office365Password
)

#Constant Variables
$OutputFile = "DistributionGroupMembers.csv"   #The CSV Output file that is created, change for your purposes
$arrDLMembers = @{}


#Remove all existing Powershell sessions
Get-PSSession | Remove-PSSession

#Did they provide creds?  If not, ask them for it.
if (([string]::IsNullOrEmpty($Office365Username) -eq $false) -and ([string]::IsNullOrEmpty($Office365Password) -eq $false))
{
    $SecureOffice365Password = ConvertTo-SecureString -AsPlainText $Office365Password -Force

    #Build credentials object
    $Office365Credentials  = New-Object System.Management.Automation.PSCredential $Office365Username, $SecureOffice365Password
}
else
{
	#Build credentials object
    $Office365Credentials  = Get-Credential
}
#Create remote Powershell session
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $Office365credentials -Authentication Basic –AllowRedirection

#Import the session
Import-PSSession $Session -AllowClobber | Out-Null

#Prepare Output file with headers
Out-File -FilePath $OutputFile -InputObject "Distribution Group DisplayName,Distribution Group Email,Member DisplayName, Member Email, Member Type" -Encoding UTF8

#Get all Distribution Groups from Office 365
$objDistributionGroups = Get-DistributionGroup -ResultSize Unlimited

#Iterate through all groups, one at a time
Foreach ($objDistributionGroup in $objDistributionGroups)
{

	write-host "Processing $($objDistributionGroup.DisplayName)..."

	#Get members of this group
	$objDGMembers = Get-DistributionGroupMember -Identity $($objDistributionGroup.PrimarySmtpAddress)

	write-host "Found $($objDGMembers.Count) members..."

	#Iterate through each member
	Foreach ($objMember in $objDGMembers)
	{
		Out-File -FilePath $OutputFile -InputObject "$($objDistributionGroup.DisplayName),$($objDistributionGroup.PrimarySMTPAddress),$($objMember.DisplayName),$($objMember.PrimarySMTPAddress),$($objMember.RecipientType)" -Encoding UTF8 -append
		write-host "`t$($objDistributionGroup.DisplayName),$($objDistributionGroup.PrimarySMTPAddress),$($objMember.DisplayName),$($objMember.PrimarySMTPAddress),$($objMember.RecipientType)"
	}
}

#Clean up session
Get-PSSession | Remove-PSSession