func runserver(t *testing.T, server *smtpd.Server) (addr string, closer func()) {
ln, err := net.Listen("tcp", "127.0.0.1:0")
if err != nil {
t.Fatalf("Listen failed: %v", err)
}
go func() {
server.Serve(ln)
}()
done := make(chan bool)
go func() {
<-done
ln.Close()
}()
return ln.Addr().String(), func() {
done <- true
}
}
