From: Wietse Venema on
The Doctor:
> Symptom: Any message with a binary attached seems
> to end up looping.
>
> Anyone here wants a sample from the logs?

No-one is interested.

You have an SMTP-based before-queue content filter that takes
minutes of time to process a file, causing the Postfix smtpd_proxy_filter
CLIENT to time out.

Per the SMTP definition, repeated timeouts will result in
REPEATED DELIVERY ATTEMPTS.

It is these MULTIPLE DELIVERY ATTEMPTS that result in multiple
deliveries.

Wietse