Adding to Albin Abel's answer:
If the Mail and Smtp Classes are used in a local code block (rather than on Class level) it may also help if you properly Dispose of them before you try to delete the file. You should do this with a Try, Finally or Using, End Using statement (in case the mail fails, you still want to Dispose of it). If you use them on Class level you should Dispose of them too, of course, just not at this particular point in your code.
parshu2378 wrote:
SmtpClient.Credentials = New Net.NetworkCredential(MailAdress, Password)
SmtpClient.Send(Mail)
Just want to say the, you should take the delivery notification, which will ensure the process flow.