using system.net.mail

I need to send thousands of emails.  I have the email addresses in an sql db.  I tested using a for loop for 100 emails.  I noticed the localhost server would only send 50 emails so I thought it was something peculiar with the dev server.  I copied the compiled site to an iis 6 site and the same number of emails is generated.  There is not a lot to go wrong with From i = 1 to 100.  Can anyone tell me what might be happening here?  I will need to send 7500 emails and I thought asp.net would be a quick and easy solution.
regards
Milton
Dim i As Integer = 1
                For i = 1 To 100
                    Dim mail As MailMessage
                &n ...