MgUserMail.ps1

<#
    Script for sending email with send-mgusermail
    
    Ref:

    https://mikecrowley.us/2021/10/27/sending-email-with-send-mgusermail-microsoft-graph-powershell
    https://docs.microsoft.com/en-us/graph/api/user-sendmail
    https://docs.microsoft.com/en-us/powershell/module/microsoft.graph.users.actions/send-mgusermail

#>

#region 1: Setup

    $emailRecipients   = @(
        'user1@domain.com'
        'user2@domain.biz'
    )
    $emailSender  = 'me@domain.info'

    $emailSubject = "Sample Email | " + (Get-Date -UFormat %e%b%Y)

    $MgConnectParams = @{
        ClientId              = '<your app>'
        TenantId              = '<your tenant id>'
        CertificateThumbprint = '<your thumbprint>'
    }

    Function ConvertTo-IMicrosoftGraphRecipient {
        [cmdletbinding()]
        Param(
            [array]$SmtpAddresses        
        )
        foreach ($address in $SmtpAddresses) {
            @{
                emailAddress = @{address = $address}
            }    
        }    
    }

    Function ConvertTo-IMicrosoftGraphAttachment {
        [cmdletbinding()]
        Param(
            [string]$UploadDirectory        
        )
        $directoryContents = Get-ChildItem $UploadDirectory -Attributes !Directory -Recurse
        foreach ($file in $directoryContents) {
            $encodedAttachment = [convert]::ToBase64String((Get-Content $file.FullName -Encoding byte))
            @{
                "@odata.type"= "#microsoft.graph.fileAttachment"
                name = ($File.FullName -split '\\')[-1]
                contentBytes = $encodedAttachment
            }   
        }    
    }

#endregion 1


#region 2: Run

    [array]$toRecipients = ConvertTo-IMicrosoftGraphRecipient -SmtpAddresses $emailRecipients 

    $attachments = ConvertTo-IMicrosoftGraphAttachment -UploadDirectory C:\tmp

    $emailBody  = @{
        ContentType = 'html'
        Content = Get-Content 'C:\tmp\HelloWorld.htm'    
    }

    Connect-Graph @MgConnectParams
    Select-MgProfile v1.0
    
    $body += @{subject      = $emailSubject}
    $body += @{toRecipients = $toRecipients}    
    $body += @{attachments  = $attachments}
    $body += @{body         = $emailBody}

    $bodyParameter += @{'message'         = $body}
    $bodyParameter += @{'saveToSentItems' = $false}

    Send-MgUserMail -UserId $emailSender -BodyParameter $bodyParameter

#endregion 2