Quoting Philip Reynolds (philip.reynolds at rfc-networks.ie):
> 1) Providing this kind of functionality at SMTP level with Postfix
> means leaving your server far more susceptible to DoS attack.
If it were not the case that the overwhelming majority of junkmail fails
other checks _before_ SA processing (such as the callbacks and DNSBLs),
you would have a good point.
I was worried about exactly that, when I first deployed sa-exim.
However, my system load actually went way _down_ rather than up, which
seemed like a pleasant surprise. As I said, the proof's in the pudding.
> Under normal circumstances, Postfix simply accepts the mail and
> stores it in the queue. Processing is done *AFTER* postfix has
> safely accepted the mail, written to disk and the remote client has
> safely disconnected. This is the most common way it is done, because
> it is the proper way to do it.
That has the unfortunate disadvantage that you cannot any longer reject
rather than bounce, and cannot perform other real-time processing that
inherently can only be performed (or only usefully performed) during the
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