I can give you all info you need.
The flow is that :
-Smartertrack try to send the notification (auto-responder)
-this addresses can't receive emails, so generate this mail back
"Delivery failed for the following recipients or groups:
flx14ea5e@scania.it
There was a problem during the delivery of the message. Try sending the message again later. If the problem persists, contact your organization's technical support.
Your message has been rejected by the following organization: 10.21.2.181."
-this mail come into Smartertrack and go inside the ticket with that message
"Queue - General Comment
The auto-responder for this Ticket was bounced"
- Smartertrack try again to send the notification... every 1-2 minutes (I expected that this retry should be done only few times)... creating an infinite loop