chore: Add a condition to handle bounced email (#11873)

Add bounced emails to the conversation thread.
Fix Gmail bounce detection by checking the X-Failed-Recipients header.

Currently, bounced emails are rejected as auto-replies, which causes
support agents to miss important delivery failure context. This PR
ensures bounced messages are correctly added to the thread, preserving
visibility for the support team.

app/mailboxes/incoming_email_validity_helper.rb

@@ -4,16 +4,17 @@ module IncomingEmailValidityHelper
   def incoming_email_from_valid_email?
     return false unless valid_external_email_for_active_account?
 
+    # Return if email doesn't have a valid sender
+    # This can happen in cases like bounce emails for invalid contact email address
+    return false unless Devise.email_regexp.match?(@processed_mail.original_sender)
+
+    # Process bounced emails, as regular emails
+    return true if @processed_mail.bounced?
+
     # 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
 

app/presenters/mail_presenter.rb

@@ -157,6 +157,10 @@ class MailPresenter < SimpleDelegator
     auto_submitted? || x_auto_reply?
   end
 
+  def bounced?
+    @mail.bounced? || @mail['X-Failed-Recipients'].try(:value).present?
+  end
+
   def notification_email_from_chatwoot?
     # notification emails are send via mailer sender email address. so it should match
     original_sender == Mail::Address.new(ENV.fetch('MAILER_SENDER_EMAIL', 'Chatwoot <accounts@chatwoot.com>')).address