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Conditional SMART_HOST IPv4/IPv6

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jkm

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Nov 13, 2009, 5:08:51 AM11/13/09
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Hi,

I run a sendmail mailserver at home together with a sixxs IPv6 tunnel
etc. Incoming mail can pass over IPv4 or IPv6 just fine. For my
outgoing IPv4 mails I have to use my ISPs smtp gateway (using
SMART_HOST in sendmail). For IPv6 I would like to use normal smtp
behavior with direct connection to the target mail server (if an IPv6
mailserver is available). Using the SMART_HOST all my outgoing mails
go through the ISPs smtp gateway so I need to split traffic depending
on if the destination mailserver has IPv6...

Is this possible?

Cheers,
/Joakim

Andrzej Adam Filip

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Nov 15, 2009, 6:17:47 AM11/15/09
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Which OS do you use?
* Linux => Have you considered using iptables to set "trasparent proxy"?

--
[pl>en Andrew] Andrzej Adam Filip : an...@onet.eu : Andrze...@gmail.com
"It's my cookie file and if I come up with something that's lame and I
like it, it goes in."
-- karl (Karl Lehenbauer)

jkm

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Nov 16, 2009, 12:54:50 PM11/16/09
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On 15 Nov, 12:17, Andrzej Adam Filip <a...@onet.eu> wrote:

> jkm <joakim.aron...@gmail.com> wrote:
> > I run a sendmail mailserver at home together with a sixxs IPv6 tunnel
> > etc. Incoming mail can pass over IPv4 or IPv6 just fine. For my
> > outgoing IPv4 mails I have to use my ISPs smtp gateway (using
> > SMART_HOST in sendmail). For IPv6 I would like to use normal smtp
> > behavior with direct connection to the target mail server (if an IPv6
> > mailserver is available). Using the SMART_HOST all my outgoing mails
> > go through the ISPs smtp gateway so I need to split traffic depending
> > on if the destination mailserver has IPv6...
>
> > Is this possible?
>
> Which OS do you use?
> * Linux => Have you considered using iptables to set "trasparent proxy"?
>
> --
> [pl>en Andrew] Andrzej Adam Filip : a...@onet.eu : Andrzej.Fi...@gmail.com

> "It's my cookie file and if I come up with something that's lame and I
> like it, it goes in."
>   -- karl (Karl Lehenbauer)

Hi Karl,

I'm using OpenBSD. Thanks for the tip, I'll have a look at that type
of solution (OpenBSD has its pf' instead of iptables).

Cheers,
/Joakim

Grant Taylor

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Nov 19, 2009, 10:17:40 PM11/19/09
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What would happen if you used your ISP's mail server as a FallBackMX
rather than a SmartHost? Wouldn't Sendmail attempt to deliver via IPv6
and then IPv4. I'm guessing that there is (or would be) an IPv4
firewall between Sendmail and the rest of the world that would cause it
to fail to be able to communicate to any IPv4 destination other than
your ISP's mail server.

Just a thought.

Grant. . . .

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