Authentication is required for relay

[Bluenose]

Hello

I am getting the following error on a forgotten.aspx page:

http://www.dimadayoub.net/forgot.aspx

Mailbox unavailable. The server response was: Authentication is required for relay

This is the code I have:

myMessage.From = New MailAddress("[e-mail]")
myMessage.To.Add(New MailAddress(strEmailValue)) 'user's email
myMessage.Subject = ("Password Reset Request")
 
myMessage.Body = ""
myMessage.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure
myMessage.IsBodyHtml = True
myMessage.Priority = MailPriority.Normal
 
HTML code to display header in email and link for user to click on to reset password
 
myMessage.AlternateViews.Add(HtmlMessage)
 
Smtpserver.DeliveryMethod = SmtpDeliveryMethod.Network
Smtpserver.Host = ("mail.server")
Smtpserver.Port = 25
Smtpserver.EnableSsl = False
Dim basicAuthenticationInfo As New System.Net.NetworkCredential("[e-mail]", "pwd")
Smtpserver.Credentials = basicAuthenticationInfo
Smtpserver.Send(myMessage)
 
myMessage.Dispose()
myMessage = Nothing
Smtpserver = Nothing

Is there anything here, please, that looks obviously wrong? I have checked with my Web hosting service, and the SMTP port, password, and host (mail.server) are correct (they work in another part of the site).

Thanks.