Microsoft Graph PowerShell脚本未读邮件附件打印筛选功能故障

开发了一款连接Microsoft Graph的PowerShell脚本，用于打印共享邮箱收件箱中未读邮件的附件。目前脚本其他功能（如下载附件、打印、标记已读）均正常，但筛选未读邮件的功能失效，无法只获取未读邮件。疑似问题出在邮件查询的URL行：

$mailUrl = "https://graph.microsoft.com/v1.0/users/$sharedMailbox/mailFolders/inbox/messages?$filter=isRead -eq $false"

Microsoft Graph的OData筛选器语法有两个关键要求：

1. 布尔值比较需使用小写的false（API对布尔值大小写敏感）
2. 比较运算符为eq（而非PowerShell的-eq）
   原脚本错误混用了PowerShell语法和Graph API的OData语法，导致筛选条件不被识别，返回了收件箱所有邮件而非仅未读邮件。

修正查询URL的筛选条件，符合OData规范：

• 将-eq替换为eq
• 确保false为小写
• 在PowerShell中用反引号`转义$符号，避免被当作变量解析

修正后的URL行：

$mailUrl = "https://graph.microsoft.com/v1.0/users/$sharedMailbox/mailFolders/inbox/messages`$filter=isRead eq false"

# Install Microsoft Graph PowerShell module if not already installed
if (-not (Get-Module -ListAvailable -Name Microsoft.Graph)) {
    Install-Module Microsoft.Graph -Scope CurrentUser -Force
}

# Define Azure App Credentials
$tenantId = "0000000000000000000000000000"
$clientId = "000000000000000000000000000000000"
$clientSecret = "00000000000000000000000000000000000"
$sharedMailbox = "emailtester@abccorp.com"

# Get Access Token
$body = @{
    grant_type    = "client_credentials"
    client_id     = $clientId
    client_secret = $clientSecret
    scope         = "https://graph.microsoft.com/.default"
} 

$tokenResponse = Invoke-RestMethod -Uri "https://login.microsoftonline.com/$tenantId/oauth2/v2.0/token" -Method Post -Body $body
$accessToken = $tokenResponse.access_token

# Fetch Emails from Shared Mailbox
$headers = @{
    Authorization = "Bearer $accessToken"
    "Content-Type" = "application/json"
}

# 修正后的筛选未读邮件URL
$mailUrl = "https://graph.microsoft.com/v1.0/users/$sharedMailbox/mailFolders/inbox/messages`$filter=isRead eq false"
$mails = Invoke-RestMethod -Uri $mailUrl -Headers $headers -Method Get

# Loop through emails and process attachments
foreach ($mail in $mails.value) {
    $mailId = $mail.id
    $attachmentsUrl = "https://graph.microsoft.com/v1.0/users/$sharedMailbox/messages/$mailId/attachments"
    $attachments = Invoke-RestMethod -Uri $attachmentsUrl -Headers $headers -Method Get

    foreach ($attachment in $attachments.value) {
        if ($attachment."@odata.type" -eq "#microsoft.graph.fileAttachment") {
            $fileName = $attachment.name
            $fileContent = [System.Convert]::FromBase64String($attachment.contentBytes)
            $filePath = "$env:TEMP\$fileName"

            # Save attachment
            [System.IO.File]::WriteAllBytes($filePath, $fileContent)
            Write-Output "Downloaded: $filePath"

            # Print the file
            Start-Process -FilePath $filePath -Verb Print
        }
    }

    # Mark email as read
    $markAsReadUrl = "https://graph.microsoft.com/v1.0/users/$sharedMailbox/messages/$mailId"
    $markAsReadBody = @{ isRead = $true } | ConvertTo-Json
    Invoke-RestMethod -Uri $markAsReadUrl -Headers $headers -Method Patch -Body $markAsReadBody
}

Write-Host "Processing Completed"

内容的提问来源于stack exchange，提问作者Matt Springer