Send an Email with Attachment using Graph API and PowerShell

I recently worked on a task to send an email with an attachment using Microsoft Graph API. The script, which is posted at the end of this blog post, sends an email to a specified email address with an attachment and also includes a table of contents in the body of the email.

I would be using an App registration in Entra ID to send an email using the Graph API. However, you can modify the script according to your own requirements and use a user account instead of an Entra app.

Prerequisites

• An Entra app with mail.send permissions.
• Client ID and Client secret values of the application.
• Tenant ID of the organization

Create App registration in Entra ID

• Sign in to the Entra admin center > Identity > Applications > App registrations.
• Click on New registration.

• Provide the display name of the application and select Accounts in this organizational directory only (<tenant> only -Single tenant). Click Register.

• Open the Entra app registration > API Permissions > Add a permission.

• Click on Microsoft Graph > Application Permissions > search for mail.send. Select Mail.send and click on Add permission.

• Click on Grant admin consent for <your org name> to grant admin consent for this application permission.

Copy Client ID, Client Secret, and Tenant ID

• Sign in to the Entra admin center > Identity > Applications > App registrations.
• Find and click the application created in the previous step.
• Click on Certificates & secrets and then click on + New client secret.
• Create a client secret and copy its value.

• Go to the Overview page of the Entra App registration and copy Client ID and tenant ID.

PowerShell Code to Send Email Using Graph API

1. Store the client ID, client secret, and tenant ID in $clientid, $clientsecret and $tenantid variables.

Client ID, Client secret, and Tenant ID

$clientid = "30ccc130-1613-4a09-8c6f-78hhsjbjekk1"
$clientsecret = "TWr8Q~yMNFKsobLjPNZ2mKo-egt8U49Hhbjdsk"
$tenantid = "97659d97-8dab-4122-80bd-caddddddd7"

2. Connect to Graph API

Connect to Graph API

#Connection to MS GRAPH API
$tokenBody = @{
    Grant_Type    = "client_credentials"
    Scope         = "https://graph.microsoft.com/.default"
    Client_Id     = $clientId
    Client_Secret = $clientSecret
}
$tokenResponse = Invoke-RestMethod -Uri "https://login.microsoftonline.com/$tenantID/oauth2/v2.0/token" -Method POST -Body $tokenBody
$headers = @{
    "Authorization" = "Bearer $($tokenResponse.access_token)"
    "Content-type"  = "application/json"
}

3. Email Attachment Variable

Next, create a variable called $attachment and provide the path of the attachment you want to send with the email. For example: $attachment = “c:\temp\listofusers.csv”. You can modify the location according to where your email attachment is stored.

Email Attachment variable

$Attachment="C:\temp\ListofUsers.csv"

4. Get File name and contents and Store them in variables $FileName and $base64string.

Get File name and contents

#Get File Name and Base64 string
$FileName=(Get-Item -Path $Attachment).name
$base64string = [Convert]::ToBase64String([IO.File]::ReadAllBytes($Attachment))

Retrieve the message parameters and convert them to JSON. $htmlobject is a PowerShell object. You can create a PowerShell object and pipe it to the ConvertTo-Html cmdlet, then use that object in the content.

The content of $htmlobject will create the email body. Also, ensure you have a sender email address stored in the $FromAddress PowerShell variable. For example: $FromAddress = “[email protected]”.

Get the message parameters and covert it to JSON

$MessageParams = @{
    "URI"         = "https://graph.microsoft.com/v1.0/users/$FromAddress/sendMail"
    "Headers"     = $headers
    "Method"      = "POST"
    "ContentType" = 'application/json'
    "Body" = (@{
          "message" = @{
          "subject" = "Userlist Report"
          "body"    = @{
               "contentType" = 'HTML' 
               "content"     = $htmloutput} 
          "toRecipients" = @(
          @{
          "emailAddress" = @{"address" = "[email protected]" }
        } )
        "attachments" = @(      
              @{      
                "@odata.type" = "#microsoft.graph.fileAttachment"
                "name" = $FileName
                "contentType" = "text/plain"
                "contentBytes" = "$base64string"          
                }        
        )
}
}) | ConvertTo-JSON -Depth 6
}

5. Send the message

The final command is to send an email using the Invoke-RestMethod command.

Invoke-RestMethod

Invoke-RestMethod @Messageparams

6. Complete PowerShell script to Send an email with attachment using Graph API

Send_Email_Attachment_Graph.ps1

#Connection to MS GRAPH API
$tokenBody = @{
    Grant_Type    = "client_credentials"
    Scope         = "https://graph.microsoft.com/.default"
    Client_Id     = $clientId
    Client_Secret = $clientSecret
}
$tokenResponse = Invoke-RestMethod -Uri "https://login.microsoftonline.com/$tenantID/oauth2/v2.0/token" -Method POST -Body $tokenBody
$headers = @{
    "Authorization" = "Bearer $($tokenResponse.access_token)"
    "Content-type"  = "application/json"
}
$Attachment=".\SPONotCompliantFileList.csv"
#Get File Name and Base64 string
$FileName=(Get-Item -Path $Attachment).name
$base64string = [Convert]::ToBase64String([IO.File]::ReadAllBytes($Attachment))
$MessageParams = @{
    "URI"         = "https://graph.microsoft.com/v1.0/users/$FromAddress/sendMail"
    "Headers"     = $headers
    "Method"      = "POST"
    "ContentType" = 'application/json'
    "Body" = (@{
          "message" = @{
          "subject" = "Userlist Report"
          "body"    = @{
               "contentType" = 'HTML' 
               "content"     = $htmloutput} 
          "toRecipients" = @(
          @{
          "emailAddress" = @{"address" = "[email protected]" }
        } )
        "attachments" = @(      
              @{      
                "@odata.type" = "#microsoft.graph.fileAttachment"
                "name" = $FileName
                "contentType" = "text/plain"
                "contentBytes" = "$base64string"          
                }        
        )
}
}) | ConvertTo-JSON -Depth 6
}
# Send the message
Invoke-RestMethod @Messageparams

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