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30 January, 2024
# Topics
Automation
Graph
PowerShell

Download O365 email Attachments with Graph

30 January, 2024
In this video I demonstrate using Microsoft Graph API to Download Office 365 email attachments and overcome the 10 emails return limit. Spoiler: Not really a limit. I use PowerShell to invoke the API and go over the setup in the Azure Portal as well.

PowerShell Script:

$connectiondetails = @{
    'tenantid' = "6c04db9b-6dd4-4cb2-9761-XXXXXXXXXXXXX"
    'Clientid' = "08a838d0-0gbc-4b82-93d9-XXXXXXXXXXXXX"
    'Clientsecret' = "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX" | ConvertTo-SecureString -AsPlainText -Force
}

$token = Get-MsalToken @connectiondetails
$accessToken = $token.AccessToken

$url = "https://graph.microsoft.com/v1.0/me/mailFolders/'long ID string'/messages"
$msgqry = $url + "?`$select=Id&`$filter=HasAttachments eq true"
$msgs = Invoke-RestMethod $msgqry -Headers @{Authorization=("bearer {0}" -f $accessToken)}

while ($msgs.value){

    foreach ($m in $msgs.value){

     $query = $url + "/" + $m.Id + "/attachments"

     $attachments = Invoke-RestMethod $query -Headers @{Authorization=("bearer {0}" -f $accessToken)}   

        foreach ($attachment in $attachments.value){
            $fname = "D:\downloads\attachments\" + $attachment.name
            $content = [System.Convert]::FromBase64String($attachment.ContentBytes)
            set-content -Path $fname -Value $content -Encoding Byte
        }

    }
    
    $msgqry = $msgs.'@odata.nextLink'
    if ($msgqry){
        $msgs = Invoke-RestMethod $msgqry -Headers @{Authorization=("bearer {0}" -f $accessToken)}
    }
    else{
        $msgs.value = ''
    }
}
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