C# Gmail API：使用包含umlauts的MailAddress会导致SMTPEception：客户端或服务器仅配置为包含ASCII本地部分的地址

尝试将带有gmail api的邮件发送到包含umlauts的邮件地址。e、 g.büro@gmail.com. 获取SmtpException，然后：

maildress: GeneralFailure: System.Net.Mail.SmtpException: The client or server is only configured for E-mail addresses with ASCII local-parts: büro@gmail.com.
bei System.Net.Mail.MailAddress.GetUser(Boolean allowUnicode)
bei System.Net.Mail.MailAddress.GetAddress(Boolean allowUnicode)
bei System.Net.Mail.MailAddress.GetSmtpAddress(Boolean allowUnicode)
bei System.Net.Mail.SmtpClient.ValidateUnicodeRequirement(MailMessage message, MailAddressCollection recipients, Boolean allowUnicode)
bei System.Net.Mail.SmtpClient.Send(MailMessage message)

我知道，当我直接使用.net smtp客户端时，您可以将SmtpDeliveryFormat.International设置为可以。但是当我使用gmail api时，如何设置它呢

private GmailService _service;

public void SendMail(MailMessage message)
{
    message.SubjectEncoding = Encoding.UTF8;
    message.BodyEncoding = Encoding.UTF8;
    message.IsBodyHtml = true;

    MimeKit.MimeMessage mimeMessage = MimeKit.MimeMessage.CreateFromMailMessage(message);
    Message sendMmessage = new Message {Raw = Base64UrlEncode(mimeMessage)};

    _service.Users.Messages.Send(sendMmessage, _fromMailAdress).Execute();
}

因为我使用的是谷歌商业账户，所以我不能直接使用SMTPClient，因为谷歌关闭了不太安全的应用程序。

我用

布鲁ro@gmail.com将解析为xn--bro-hoa@gmail.com

请参见以下内容：

IdnMapping idn = new IdnMapping();

MailMessage message = new MailMessage
{
    From = new MailAddress(_fromMailAdress),
};
message.BodyEncoding = Encoding.UTF8;
message.IsBodyHtml = true;
message.To.Add(idn.GetAscii(toMailAdress));
message.Subject = subject;
message.Body = content;