Email loop protection - bounce mails

when you have external agents with email notification turned on.
and the external mailbox has trouble - then you can run into an email loop

had this scenario:

  1. zammad notification -->
  2. bounce email --> zammad ticket
  3. zammad notification -->
  4. bounce email --> zammad ticket


most email systems can detect this mail loops and stop it.

maybe the already existing email filters are a starting point.

But the first incoming bounce mail should not be blocked…

Sorry but I don’t seem to understand the issue?
Bounces can occur for various reasons and how they’re handled can also be a question of configuration.

I really try to understand your issue, please describe what the issue is.

I had the following issue:

  1. zammad notification to external agent -->
  2. External Agent mailbox had a problem and sent a bounce mail --> zammad ticket
  3. The bounce mail was an new ticket aricel and generatet a new notification -->
  4. the external mailbox problem still exists and so the next bounce mail was sent --> zammad ticket
  5. The bounce mail was an new ticket aricel and generatet a new notification -->
  6. …this steps repeat in an loop until something crash - eg. disk full

That’s no feature request and technically correct behaviour by Zammad.
The reason for that is that a bounce never contains reference information that would help Zammad to recognize e.g. follow ups.

Also, technically, there’s no loop happening here. Those mails you’re talking about are triggered based on the notification settings of the affected agent and might be independent.

You can’t overcome this issue, because Zammad can’t determine why the bounce occured.
That’s nothing we can solve, sorry.

Thanks for your input MrGeneration, I understand that this is not illegal behavior, but it does create a flood storm.

I have seen other ticketing systems implement flood protection with exponential backoff, e.g. if a customer submits $NUMBER of tickets in $TIME then flood protection will reject further tickets for $WAIT_PERIOD.

More advanced solutions will increase $WAIT_PERIOD according to an exponential scale (or Fibonacci sequence) if flood protection is triggered within $WAIT_PEROIOD+$TIME.

This is how Zendesk does it for example: About mail loops and Zendesk email – Zendesk help

@Will that’s clearly a feature request and should be categorized as such in your very own thread.

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