List all external users in all site collections

$fileExportPath = "<PUTYOURPATHHERE.csv>"

Connect-SPOService https://<yourorg>-admin.sharepoint.com

$results = @()
Write-host "Retrieving all sites and check external users..."
$allSPOSites = Get-SPOSite -Limit ALL
$siteCount = $allSPOSites.Count

Write-Host "Processing $siteCount sites..."
#Loop through each site
$siteCounter = 0

foreach ($site in $allSPOSites) {
  $siteCounter++
  Write-Host "Processing $($site.Url)... ($siteCounter/$siteCount)"

  Write-host "Retrieving all external users ..."

  $users = Get-SPOExternalUser -SiteUrl $($site.Url)

  Write-host "  $($users.Count) external users ..." -ForegroundColor Yellow

  foreach ($user in $users) {
    
    $results = [pscustomobject][ordered]@{
      DisplayName = $user.DisplayName
      Email       = $user.Email
      WhenCreated = $user.WhenCreated
      Url         = $site.Url
    }

    $results | Export-Csv -Path $fileExportPath -NoTypeInformation -Append
  }
}


Write-Host "Completed."

#Global Variable Declaration
$AdminURL = "https://domain-admin.sharepoint.com/"
$TenantURL = "https://domain.SharePoint.com"
$UserName = "chandani@domain.onmicrosoft.com"
$Password = "********"
$SecureStringPwd = $Password | ConvertTo-SecureString -AsPlainText -Force 
$Credentials = New-Object System.Management.Automation.PSCredential -ArgumentList $UserName, $SecureStringPwd
$DateTime = "_{0:MM_dd_yy}_{0:HH_mm_ss}" -f (Get-Date)
$BasePath = "E:\Contribution\PnP-Scripts\GetExtenalUsers\Logs\"
$CSVPath = $BasePath + "\ExternalUsers" + $DateTime + ".csv"
$global:ExternalUsersData = @() 
Function LoginToAdminSite() {
    [cmdletbinding()]
    param([parameter(Mandatory = $true, ValueFromPipeline = $true)] $Credentials)
    Write-Host "Connecting to Tenant Admin Site '$($AdminURL)'..." -ForegroundColor Yellow
    Connect-PnPOnline -Url $AdminURL -Credentials $Credentials
    Write-Host "Connection Successfull to Tenant Admin Site :'$($AdminURL)'" -ForegroundColor Green
}
Function ConnectToSPSite() {
    try {
        $SiteCollection = Get-PnPTenantSite -Filter "Url -like '$TenantURL'" | Where { $_.SharingCapability -ne "Disabled" }
        foreach ($Site in $SiteCollection) {
            $SiteUrl = $Site.Url    
            Write-Host "Connecting to Site :'$($SiteUrl)'..." -ForegroundColor Yellow  
            Connect-PnPOnline -Url $SiteUrl -Credentials $Credentials
            Write-Host "Connection Successfull to site: '$($SiteUrl)'" -ForegroundColor Green              
            GetExternalUsers($SiteUrl)                        
        }
        ExportData       
    }
    catch {
        Write-Host "Error in connecting to Site:'$($SiteUrl)'" $_.Exception.Message -ForegroundColor Red               
    } 
}
Function GetExternalUsers($siteUrl) {
    try {
        $ExternalUsers = Get-PnPUser | Where { $_.LoginName -like "*#ext#*" -or $_.LoginName -like "*urn:spo:guest*" }   
        Write-host "Found '$($ExternalUsers.count)' External users" -ForegroundColor Gray
        ForEach ($User in $ExternalUsers) {
            $global:ExternalUsersData += New-Object PSObject -Property ([ordered]@{
                    SiteName  = $site.Title
                    SiteURL   = $SiteUrl
                    UserName  = $User.Title
                    Email     = $User.Email
                    LoginName = $User.LoginName
                })
        }          
    }
    catch {
        Write-Host "Error in getting external users :'$($siteUrl)'" $_.Exception.Message -ForegroundColor Red                 
    }        
}

Function ExportData {
    Write-Host "Exporting to CSV" -ForegroundColor Yellow           
    $global:ExternalUsersData | Export-Csv -Path $CSVPath -NoTypeInformation -Append
    Write-Host "Exported Successfully!" -ForegroundColor Green 
}

Function StartProcessing {   
    LoginToAdminSite($AdminURL) 
    ConnectToSPSite
}

StartProcessing