C# 通过Exchange发送邮件问题

乙方，需要在其他公司内部服务器做一个用Exchange发送邮件的小程序
之前的账号没了，分不多了，全给出来了
代码如下：

            ExchangeVersion version = ExchangeVersion.Exchange2010;
            ExchangeService service = new ExchangeService(version);
            ServicePointManager.ServerCertificateValidationCallback = delegate(
                     object sender,
                     X509Certificate certificate,
                     X509Chain chain,
                     SslPolicyErrors sslPolicyErrors)
            {
                return true;
            };

            service.Credentials = new NetworkCredential(setting.Account, setting.Password, setting.Domain);
            service.TraceEnabled = true;
            if (!String.IsNullOrEmpty(setting.Server))
                service.Url = new Uri(setting.Server);
            else
                service.AutodiscoverUrl(setting.Address, new Microsoft.Exchange.WebServices.Autodiscover.AutodiscoverRedirectionUrlValidationCallback(url => true));

            EmailMessage emessage = new EmailMessage(service);
            emessage.Subject = message.Subject;
            emessage.ToRecipients.AddRange(message.To.Select(o => o.Address));
            emessage.Body = new MessageBody() { BodyType = BodyType.HTML, Text = (message.Body.Replace("\n", "<br />")).Replace("\r\n","<br />") };

            emessage.SendAndSaveCopy();

如果用AutodiscoverUrl，直接就报错“The Autodiscover service couldn't be located"
他们IT帮配置的outlook上是可以正常发送邮件的，我发现他们设置了代理服务器，身份验证方式选的NTML。。我用代理服务器的地址加上“/EWS/Exchange.asmx”放进URL，报错就变成了 403 forbidden了。。。问甲方IT，他们IT说OUTLOOK能发就不管了。。。跪求

顶一下自己，哎，我也知道这个问题很少见，我网上都查不到