email recognizes as Junk

[Shahid]

Hi everybody,
In my windows application i have a functunality to send mails to users (
i've done this many times )
The problem that i have right now is that these messages are recognized as
Junk Mail from Microsoft Outlook 2003
I've tried to manage the headers but with no luck
are there some rules that can be keep to mails not goin' as a Junk Mail

here is the Code
===========

Dim oMsg As New System.Net.Mail.MailMessage
Dim oFromAddress As New
System.Net.Mail.MailAddress("Sh****@global.com.kw" , "Global Investment House
- Kuwait", System.Text.ASCIIEncoding.ASCII)
Dim oToAddress As New
System.Net.Mail.MailAddress("sh****@Global.com.kw" , "Shahid")

oMsg.From = oFromAddress
oMsg.To.Add("sh****@global.com.kw")
oMsg.Subject = "Subject"
oMsg.IsBodyHtml = True
oMsg.Headers.Add("Content-Type", "text/html;
charset=""windows-1251""")
oMsg.Headers.Add("Message-ID", "sh****@global.com.kw")
oMsg.Headers.Add("Delivery-Notification-To",
"Sh****@global.com.kw")
oMsg.Headers.Add("Return-Receipt-To", "sh****@global.com.kw")
oMsg.Body = "Please Click here to visit site
http://www.globalinv.net"

smtpServer.Send(oMsg)

Thanks
Shahid