发邮件时的防火墙如何设置？

[morningnet]

我使用东方卫士的防火墙，如果防火墙关闭的话，用．net做的发邮件没有任何问题．代码如下：
Dim mailObj As New SmtpClient("smtp.163.com")
mailObj.Credentials = New System.Net.NetworkCredential("[e-mail]", "211111111")
Dim mailMessObj As New MailMessage()
mailMessObj.From = New MailAddress("[e-mail]", "系统管理员")
mailMessObj.To.Add(Trim(txtemail.Text))
mailMessObj.Subject = "系统密码"
mailMessObj.Body = "你的新密码为:" + pwd0 + ".请尽快修改你的密码."
mailMessObj.Priority = MailPriority.High
mailObj.Send(mailMessObj)


但是一旦开启防火墙,即使是使用最低的安全级别,也会出现错误:
System.Net.Mail.SmtpException: Failure sending mail. ---> System.IO.IOException: Unable to write data to the transport connection: 从来不应失败的系统调用失败了。. ---> System.Net.Sockets.SocketException: 从来不应失败的系统调用失败了。 at System.Net.Sockets.Socket.Send(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags) at System.Net.Sockets.NetworkStream.Write(Byte[] buffer, Int32 offset, Int32 size) --- End of inner exception stack trace --- at System.Net.Sockets.NetworkStream.Write(Byte[] buffer, Int32 offset, Int32 size) at System.Net.PooledStream.Write(Byte[] buffer, Int32 offset, Int32 size) at System.Net.Mail.SmtpConnection.Flush() at System.Net.Mail.CheckCommand.Send(SmtpConnection conn, String& response) at System.Net.Mail.DataStopCommand.Send(SmtpConnection conn) at System.Net.Mail.SmtpConnection.OnClose(Object sender, EventArgs args) at System.Net.ClosableStream.Close() at System.Net.Mail.MailWriter.Close() at System.Net.Mail.SmtpClient.Send(MailMessage message) --- End of inner exception stack trace --- at System.Net.Mail.SmtpClient.Send(MailMessage message) at erecallpwd.Button2_Click(Object sender, EventArgs e)

请问放火墙如何设置?,我的25,110端口都是开放的.