Send Emails To Multiple Address?

how can i retry sending failed email recipients. i am trying to make an application in vbnet where i can send emails to multiple address. some code snippet:

Dim SmtpServer As New SmtpClient()
SmtpServer.Credentials = New Net.NetworkCredential(xInformation(0), xInformation(1))
SmtpServer.Port = CInt(xInformation(2))

[code]...

question arises:

1.) if i have to send, for instance, email to 5 recipients, and only 3 emails have been successfully sent, how can i know the failed email addresses?

2.) where is the failed email address stored?

3.) what exceptions are needed to trapped this error?