要获取Exchange EmailMessage的属性，您可以使用Exchange Web Services (EWS) API。以下是一个示例代码，演示如何获取EmailMessage的属性并检查是否转发过：

using Microsoft.Exchange.WebServices.Data;

// 创建ExchangeService实例
ExchangeService service = new ExchangeService(ExchangeVersion.Exchange2010_SP2);
service.Credentials = new WebCredentials("your-email@example.com", "your-password");
service.Url = new Uri("https://your-exchange-server/EWS/Exchange.asmx");

// 获取邮件
EmailMessage email = EmailMessage.Bind(service, new ItemId("email-id"));

// 检查转发状态
bool forwarded = email.IsAssociated;

// 打印邮件属性
Console.WriteLine("Subject: " + email.Subject);
Console.WriteLine("From: " + email.From.Name);
Console.WriteLine("To: " + email.DisplayTo);
Console.WriteLine("Forwarded: " + forwarded);

在上述示例中，您需要替换以下内容：

• "your-email@example.com"：您的Exchange邮箱地址。
• "your-password"：您的Exchange邮箱密码。
• "https://your-exchange-server/EWS/Exchange.asmx"：您的Exchange服务器的URL。
• "email-id"：要检查属性的EmailMessage的ID。

请注意，此示例假设您已经安装了Exchange Web Services Managed API。您可以通过NuGet包管理器安装Microsoft.Exchange.WebServices来获取该API。

希望这可以帮助到您！