I have the following problem:
Suppose there is a mail system (based on Zimbra) with a user that set up a filter to forward all mails to an external account. When mail arrives to Zimbra it is correctly forwarded to the external mail system, but suppose that the external mail account is out of quota.
What happens is that the external mail system produces a reply warning Zimbra that the receiving account is out of quota to Zimbra but (as I could see) it removes X-Zimbra-Forwarded header as it produces a new mail, so when that mail is received by Zimbra it is forwarded again to the external account starting in this way an infinite loop.
My question is: Is there any way to avoid forwarding out-of-quota emails or it is a user responsibility to filter them?