Log mail delivery errors to database and add an UI for it

app/controllers/admin/mail_delivery_status_controller.rb

@@ -0,0 +1,30 @@
+class Admin::MailDeliveryStatusController < Admin::BaseController
+  inherit_resources
+
+  def index
+    @maildeliverystatus = MailDeliveryStatus.order(created_at: :desc)
+    @maildeliverystatus = @maildeliverystatus.where(email: params[:email]) unless params[:email].blank?
+    @maildeliverystatus = @maildeliverystatus.page(params[:page]).per(@per_page)
+  end
+
+  def show
+    @maildeliverystatus = MailDeliveryStatus.find(params[:id])
+    filename = "maildeliverystatus_#{params[:id]}.#{MIME::Types[@maildeliverystatus.attachment_mime].first.preferred_extension}"
+    send_data(@maildeliverystatus.attachment_data, :filename => filename, :type => @maildeliverystatus.attachment_mime)
+  end
+
+  def destroy_all
+    @maildeliverystatus = MailDeliveryStatus.delete_all
+    redirect_to admin_mail_delivery_status_index_path, notice: t('.notice')
+  rescue => error
+    redirect_to admin_mail_delivery_status_index_path, alert: I18n.t('errors.general_msg', msg: error.message)
+  end
+
+  def destroy
+    @maildeliverystatus = MailDeliveryStatus.find(params[:id])
+    @maildeliverystatus.destroy
+    redirect_to admin_mail_delivery_status_index_path, notice: t('.notice')
+  rescue => error
+    redirect_to admin_mail_delivery_status_index_path, I18n.t('errors.general_msg', msg: error.message)
+  end
+end