Why you should use :fail: – addendum

I have added the following to the Why you should use :fail: page on our site:

Causes emails that will never be delivered onto the exim mail queue because checks such as sender verification are still carried out when processing such emails and if they cannot complete they will stay on the exim mail queue and repeatedly reprocess the email until it is finally discarded (usually 4+ days). This can cause very large mail queues full of spam which is repeatedly processed causing severe performance degradation