Re: MTA comparison (postfix, exim4, ...)

[MJ Ray <mjr@phonecoop.coop>]

Michael Alan Dorman <mdorman@tendentious.org> wrote: [...]
> Still, if not...well, I wrote an event-driven postfix policy daemon in
> perl using POE that's able to handle > 100 queries/second on consumer
> hardware in a few dozen lines of code.

Thanks for the pointers.  Can a policy server delay an incoming mail?
I suspect that sleeping in the perl would delay all incoming mail and
there's no access(5) response like Exim's delay, else I could do it
another way.  How can it be done?  (I want to increase the connection
cost to maybe-spammers of sending to my postfix...)

> MJ Ray <mjr@phonecoop.coop> wrote:
> > 2. when an email that I'm forwarding (due to /etc/aliases or a
> > .forward or whatever) comes in, can I start trying to send it straight
> > out and SMTP-reject it if the remote host doesn't want it?  [...]
>
> I believe http://www.postfix.org/ADDRESS_VERIFICATION_README.html
> details the facility you're looking for.

I don't believe it does.  I don't want to verify the recipient address
- I want to try delivering the redirected mail and avoid being left
holding the baby if the destination MX doesn't want it or is MIA.

About Bernd Zeimetz's comment: I think it's not a way to DoS any more
than delivering directly to the destination MX is a way to DoS.
Sending hosts generally can't tell that the message is being
redirected and they'd be caught in neg-exp rate limits for trying to
send too much bad mail before it becomes a DoS on most hosts, as well
as whatever the target MX is doing.  Even so, redirecting mail is
discouraged because it increases the number of links in the chain.

Thanks for the comments,
-- 
MJ Ray http://mjr.towers.org.uk/email.html tel:+44-844-4437-237 -
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