Serializza gli invii SMTP su una coda unica per non far chiudere Aruba.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/models/mailing_recipient.rb

@@ -71,32 +71,70 @@ class MailingRecipient < ApplicationRecord
     MailMerge.render(mailing.subject_for(ab_variant), **merge_context)
   end
 
-  def deliver!
+  def queued?
+    status == "queued"
+  end
+
+  def enqueue_for_delivery!
+    Mailings::OutboundQueue.enqueue(self)
+  end
+
+  def deliver_queued!
     with_lock do
       return if status.in?(%w[sent skipped])
       return abort_delivery!("invio annullato") unless mailing.sending?
-
-      update!(status: "queued")
+      return unless queued?
     end
 
-    return unless mailing.sending?
-
     html = rendered_html
     subject_line = rendered_subject_line
-    CampaignMailer.outreach(self, html: html, subject: subject_line).deliver_now
+    Mailings::SmtpGate.deliver do
+      CampaignMailer.outreach(self, html: html, subject: subject_line).deliver_now
+    end
     record_success!(subject_line)
+    :sent
+  rescue *Mailings::SmtpGate::RETRYABLE => e
+    defer_or_fail!(e)
   rescue StandardError => e
     update!(status: "failed", error_message: e.message.to_s.truncate(500))
+    :failed
   ensure
     mailing.mark_finished_if_done!
   end
 
+  def deliver!
+    enqueue_for_delivery!
+    deliver_queued! if queued?
+  end
+
   private
 
   def abort_delivery!(reason)
     update!(status: "skipped", skip_reason: reason)
   end
 
+  MAX_SMTP_DEFERS = 8
+  DEFER_PATTERN = /tentativo (\d+)\//
+
+  def defer_or_fail!(error)
+    attempt = smtp_defer_count + 1
+    message = error.message.to_s.truncate(400)
+    if attempt >= MAX_SMTP_DEFERS
+      update!(status: "failed", error_message: message)
+      :failed
+    else
+      update!(
+        status: "queued",
+        error_message: "Da ritentare (#{attempt}/#{MAX_SMTP_DEFERS}): #{message}"
+      )
+      :deferred
+    end
+  end
+
+  def smtp_defer_count
+    error_message.to_s[DEFER_PATTERN, 1].to_i
+  end
+
   def record_success!(subject_line)
     transaction do
       update!(status: "sent", sent_at: Time.current, rendered_subject: subject_line, error_message: nil)