Share a SharePoint Online site using a custom HTML email

BulkShareWithCustomEmail.ps1

[CmdletBinding(DefaultParameterSetName="UseCSV")]
Param(
    [Parameter(Mandatory=$true, Position=0, ParameterSetName="UseCSV", HelpMessage="This is the path to the CSV file that has a single column, Email, which contains each email address to be invited.")]
    [string]$CSVFile,

    [Parameter(Mandatory=$true, Position=0, ParameterSetName="UseEmail", HelpMessage="This is the email address to be invited.")]
    [string]$UserEmail,

    [Parameter(Mandatory=$false, ParameterSetName="UseEmail", HelpMessage="This is the URL to the SharePoint Online site where you are inviting users.")]
    [Parameter(Mandatory=$false, ParameterSetName="UseCSV", HelpMessage="This is the URL to the SharePoint Online site where you are inviting users.")]
    [string]$Url, 

    [Parameter(Mandatory=$false, ParameterSetName="UseEmail", HelpMessage="This is the display name of the group on your SharePoint Online site where users will be added.")]
    [Parameter(Mandatory=$false, ParameterSetName="UseCSV", HelpMessage="This is the display name of the group on your SharePoint Online site where users will be added.")]
    [string]$GroupTitle,

    [Parameter(Mandatory=$false, ParameterSetName="UseEmail", HelpMessage="This is the path to the DLLs for CSOM.")]
    [Parameter(Mandatory=$false, ParameterSetName="UseCSV", HelpMessage="This is the path to the DLLs for CSOM.")]
    [string]$CSOMPath,

    [Parameter(Mandatory=$false, ParameterSetName="UseEmail", HelpMessage="This is the subject of the email that is sent to the users being invited.")]
    [Parameter(Mandatory=$false, ParameterSetName="UseCSV", HelpMessage="This is the subject of the email that is sent to the users being invited.")]
    [string]$EmailSubject,

    [Parameter(Mandatory=$false, ParameterSetName="UseEmail", HelpMessage="This is the path to the HTML file containing the body of the email sent to the users being invited.")]
    [Parameter(Mandatory=$false, ParameterSetName="UseCSV", HelpMessage="This is the path to the HTML file containing the body of the email sent to the users being invited.")]
    [string]$EmailBodyFile,


    [Parameter(Mandatory=$false, ParameterSetName="UseCSV", HelpMessage="This is the number of email addresses to include in one batch.")]
    [int]$BatchAmount,

    [Parameter(Mandatory=$false, ParameterSetName="UseCSV", HelpMessage="This is the amount of seconds to wait between batches.")]
    [int]$BatchInterval
)

Set-Strictmode -Version 1

If ($CSOMPath -eq $null -or $CSOMPath -eq "") { $CSOMPath = "." }
If ($GroupTitle -eq $null -or $GroupTitle -eq "") { $GroupTitle = "REDACTED" }
If ($Url -eq $null -or $Url -eq "") { $Url = "REDACTED" }
If ($EmailSubject -eq $null -or $EmailSubject -eq "") { $EmailSubject = "REDACTED" }
If ($EmailBodyFile -eq $null -or $EmailBodyFile -eq "") { $EmailBodyFile = "REDACTED" }

Add-Type -Path "$CSOMPath\Microsoft.SharePoint.Client.dll" 
Add-Type -Path "$CSOMPath\Microsoft.SharePoint.Client.Runtime.dll" 

If ($PSCmdlet.ParameterSetName -eq "UseCSV") {
    $usersCSV = Import-CSV $CSVFile
    If ($BatchAmount -eq $null -or $BatchAmount -lt 0) { $BatchAmount = 30 }
    If ($BatchInterval -eq $null -or $BatchInterval -lt 0) { $BatchInterval = 60 }
} Else {
    $BatchAmount = 1
    $BatchInterval = 0
    $usersCSV = @(@{
        "Email"="$UserEmail";
    })
}

# connect/authenticate to SharePoint Online and get ClientContext object.. 
$psCredentials = Get-Credential
$spoCredentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($psCredentials.UserName, $psCredentials.Password)
$clientContext = New-Object Microsoft.SharePoint.Client.ClientContext($Url) 
$clientContext.Credentials = $spoCredentials 

$domain = ([System.Uri]$Url).Host
$userName = $psCredentials.UserName

If ($clientContext.ServerObjectIsNull.Value) { 
    Write-Error "Could not connect to SharePoint Online site collection: $Url"
} Else {
    Write-Host "Connected to SharePoint Online site collection: " $Url -ForegroundColor Green        
                
    $web = $clientContext.Web
    $clientContext.Load($web)
    $clientContext.Load($web.SiteGroups)
    $clientContext.ExecuteQuery()

    $myGroups = $web.SiteGroups | ? { $_.Title -eq $GroupTitle }
    If ($myGroups.Count -eq 0) { 
        Write-Error "Group, $GroupTitle, was not found." 
    } Else {
        $myGroups | % {
            $groupNumber = $_.Id
            Write-Host "Found ID for `"$GroupTitle`": " $groupNumber -ForegroundColor Green        

            $EmailBodyTemplate = ""
            Get-Content $EmailBodyFile | % { $EmailBodyTemplate += $_ }
            Write-Host "Template, $EmailBodyFile, has been imported." -ForegroundColor Green        

            $i = 0
            $usersCSV | % { 
                Add-Member -InputObject $_ -MemberType NoteProperty -Name "Row" -Value $i; $i++ 
            } 
            $usersCSV | Group-Object { 
                [System.Math]::Truncate($_.Row / $BatchAmount) 
            } | % {
                Write-Host "--- Start of Batch ---"
                $_.Group | % { 
                    $email = $_.Email

                    Write-Host "Inviting user: " $email -ForegroundColor Green     
                    $peoplePickerValue = "[{`"Key`":`"$email`",`"Description`":`"$email`",`"DisplayText`":`"$email`",`"EntityType`":`"`",`"ProviderDisplayName`":`"`",`"ProviderName`":`"`",`"IsResolved`":true,`"EntityData`":{`"SPUserID`":`"$email`",`"Email`":`"$email`",`"IsBlocked`":`"False`",`"PrincipalType`":`"UNVALIDATED_EMAIL_ADDRESS`",`"AccountName`":`"$email`",`"SIPAddress`":`"$email`"},`"MultipleMatches`":[],`"AutoFillKey`":`"$email`",`"AutoFillDisplayText`":`"$email`",`"AutoFillSubDisplayText`":`"`",`"AutoFillTitleText`":`"$email\n$email`",`"DomainText`":`"$domain`",`"Resolved`":true}]"
                    $sharingResult = [Microsoft.SharePoint.Client.Web]::ShareObject($clientContext, $Url, $peoplePickerValue, "group:$groupNumber", $groupNumber, $false, $false, $false, "", "", $true)
                    $clientContext.Load($sharingResult)
                    $clientContext.ExecuteQuery()

                    Write-Host "Emailing user: " $email -ForegroundColor Green        
                    $invitationLink = $sharingResult.InvitedUsers[0].InvitationLink
                    $todaysDate = Get-Date -Format D

                    $EmailBody = $EmailBodyTemplate.ToString().Replace("`$invitationLink", "$invitationLink").Replace("`$todaysDate", "$todaysDate")
                    Send-MailMessage -To $email -From $userName -Subject $EmailSubject -Body $EmailBody -BodyAsHtml -SmtpServer smtp.office365.com -UseSsl -Credential $psCredentials -Port 587
                }
                Write-Host "--- End of Batch ---"
                Start-Sleep -Seconds $BatchInterval
            }
        }
    }
}