I'm not sure that GC would matter very much in such a simple app.
But, it's either a call to
Dispose on your
SmtpClient after you're done using it:
or use a
using (SmtpClient smtp = new SmtpClient
Host = "smtp.gmail.com",
Port = 587,
Credentials = new NetworkCredential("firstname.lastname@example.org", "password"),
EnableSsl = true
using will take care of calling
Dispose for you.
Also, don't forget that there's a convenience method on the
SmtpClient, if you don't need anything fancy on the message like HTML formatting or attachments.
smtp.Send(from, to, subject, body);