审批流设置邮件接收，查看系统日志发现报错，收不到邮件

用户cloud@lhglass.com发送邮件到chenyang.yan@lhglass.com失败。详细信息：
错误消息: Mailbox unavailable. The server response was: Connection refused;
错误类型：System.Net.Mail.SmtpException;
错误堆栈： at System.Net.Mail.SmtpConnection.GetConnection(ServicePoint servicePoint)
at System.Net.Mail.SmtpClient.Send(MailMessage message)
at Kingdee.BOS.Util.MailUtils.Sendmail(String from, String displayName, List`1 toList, String subject, String body, String SMTPHost, Int32 port, Boolean enableSSL, Dictionary`2 dictStream, String userName, String pass)
at Kingdee.BOS.Workflow.ActionEvents.EmailProvider.SendEmail(Context context, Message msg, String userName, String pass, MailFrom mailFrom);