症状
使用 Set-ExchangeServer -InternetWebProxy cmdlet 在 Microsoft Exchange Server 2019 中配置代理服务器后，新式附件功能将不起作用。 如果在 Outlook 网页版 (OWA) 发送具有新式附件的电子邮件，则会记录以下事件：
From: Microsoft Outlook <microsoftexchange329e71ec88ae4615bbc36ab6ce41109e@contoso.com>
To: <the user who just sent out a modern attachment>
Subject: Your recipients couldn't be given access to the file <file name>
Body: The location where the file is stored isn't available.
The message was sent, but recipients might not be able to access the attachment.
Try opening the file <filename> and giving others access to it from its current location.
解决方法
若要解决此问题，请安装以下累积更新：
Exchange Server 2019 的累积更新 14 或 2019 Exchange Server的更高版本累积更新