improve SMTP configs form

spec/mailers/previews/settings_mailer_preview.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class SettingsMailerPreview < ActionMailer::Preview
+  def smtp_successful_setup
+    SettingsMailer.smtp_successful_setup('example@gmail.com')
+  end
+end