chore: Stop processing auto-response emails (#9606)

Stop processing auto-response emails
https://www.notion.so/chatwoot/Avoid-Auto-Replies-sorcerer-s-apprentice-mode-55ffb09efbd7451994f1ff852de4c168?pvs=4

app/mailboxes/incoming_email_validity_helper.rb

@@ -0,0 +1,35 @@
+module IncomingEmailValidityHelper
+  private
+
+  def incoming_email_from_valid_email?
+    return false unless valid_external_email_for_active_account?
+
+    # we skip processing auto reply emails like delivery status notifications
+    # out of office replies, etc.
+    return false if auto_reply_email?
+
+    # return if email doesn't have a valid sender
+    # This can happen in cases like bounce emails for invalid contact email address
+    # TODO: Handle the bounce separately and mark the contact as invalid in case of reply bounces
+    # The returned value could be "\"\"" for some email clients
+    return false unless Devise.email_regexp.match?(@processed_mail.original_sender)
+
+    true
+  end
+
+  def valid_external_email_for_active_account?
+    return false unless @account.active?
+    return false if @processed_mail.notification_email_from_chatwoot?
+
+    true
+  end
+
+  def auto_reply_email?
+    if @processed_mail.auto_reply?
+      Rails.logger.info "is_auto_reply? : #{processed_mail.auto_reply?}"
+      true
+    else
+      false
+    end
+  end
+end