Hi !
Not use what you outgoing mail volume is, but you could write a 'simple' external program which connects to the destination server,
does a rcpt verify and based upon that returns true of false.
You could then use this program in a $condition in a manualroute router ..... ( i suppose )
bye,
Chris
----- Original Message -----
From: "Andrew McGill" <andrew2005@???>
To: <exim-users@???>
Sent: Wednesday, June 15, 2005 1:40 PM
Subject: [exim] Send direct, but use ISP relay if any error occurs
> Hi there
>
> With apologies to the purists and the RFCs ...
>
> We are sending mail for a LAN from a dynamic IP address. Some
> DNS blacklists list our IP address as evil, so some people will
> not accept mail directly from us (because our neighbours and ISP
> are irresponsible).
>
> Our ISP will relay mail for us, but occasionally they have long
> queues (4 hours), and strange errors, which we want to avoid
> wherever possibe. It is also impossible to trace the state /
> fate of mail submitted to the ISP relay. Ocasionally the ISP
> changes the rules on their server causing support calls (no
> bounces, max_recipients, no yahoo+other, blah). There is no
> other ISP, and no convenient point to set up a non-fussy relay.
>
> We want to deliver outgoing mail with the following strategy:
>
> 1. Attempt to deliver mail directly to destination.
>
> 2. If (1) fails for *any* reason (452 DNS blacklisted, 550 DNS
> blacklist, DNS failure, or TCP timeout) then treat this as a
> temporary failure and retry immediately using the ISP mail
> spooler.
>
> One way of implementing this is to have a transparent proxy for
> outgoing TCP/25 connections that transforms every 55x to 45x in
> reply codes, and then diverts future connections to the same IP
> via the ISP server. That's rather messy and platform dependant.
>
> I'm hoping for something like fallback_hosts, together with a
> soft-fail option (which doesn't seem to exist) to convert "550
> blocked by acmeRBL" to "450 blocked by acmeRBL" .. or maybe ..
>
> lookuphost:
> driver = lookuphost
> transport = careful_smtp
> # We'd prefer to do it this way ...
>
> smarthost:
> driver = domainlist
> transport = remote_smtp
> route_list = "* smtp.sentechsa.com bydns_a"
> # Yuck. Only if I have to!
>
> ...
>
> careful_smtp:
> driver = smtp
> response_pattern = ^2
> # Only accept happy responses? Well, that's for the iplookup
> # driver ... I don't think that'll work ...
>
> &:-)
>
>
> ps. You can do this with bleeding edge postfix .. well, mostly.
>
> --
> DiSCOvery fiaSCO underSCOres miSCOnceived diSCOntent
> (groklaw.net)
>
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>
>
