multiple transport maps for same destination

[Luigi Rosa]

Given a mail server with latest Postfix and a transport map like this for some
domains that routes the delivery thru ISP MTA:

domain1.com relay:[isp.mta.com]
domain2.com relay:[isp.mta.com]
domain3.com relay:[isp.mta.com]

ISP (is a big one) says that since sometimes his MTA is listed in some RBL we
can try with another MTA as a fallback or round-robin

If I put something like this

domain1.com relay:[isp.mta.com]
domain2.com relay:[isp.mta.com]
domain3.com relay:[isp.mta.com]
domain1.com relay:[isp.mtabak.com]
domain2.com relay:[isp.mtabak.com]
domain3.com relay:[isp.mtabak.com]

Postfix uses always the second entry.

Is there a way to tell Postfix to use one and if the connection fails use the
other, just like a DNS MX weight?

Thank you

--


Ciao,
luigi

/
+--[Luigi Rosa]--
\

Don't focus on the one guy who hates you. You don't go to the park
and set your picnic down next to the only pile of dog shit.

[Viktor Dukhovni]

On Mon, May 11, 2015 at 04:32:31PM +0200, Luigi Rosa wrote:

> Given a mail server with latest Postfix and a transport map like this for
> some domains that routes the delivery thru ISP MTA:
>
> domain1.com relay:[isp.mta.com]
> domain2.com relay:[isp.mta.com]
> domain3.com relay:[isp.mta.com]
>
> ISP (is a big one) says that since sometimes his MTA is listed in some RBL
> we can try with another MTA as a fallback or round-robin

This advice is bad. Any problems with RBLs manifest *after* the
destination relay has accepted your mail. Therefore adding a
failback does no good. All the mail goes to the primary anyway.

However, they can if they wish publish MX records or multiple A
records (simplest if the relay is also a submission service for
MUAs) for their relay service, and disable any IPs that correspond
to blacklisted nodes. They should also do a better job of filtering
outbound spam and avoid getting blacklisted.

> If I put something like this
>
> domain1.com relay:[isp.mta.com]
> domain2.com relay:[isp.mta.com]
> domain3.com relay:[isp.mta.com]
> domain1.com relay:[isp.mtabak.com]
> domain2.com relay:[isp.mtabak.com]
> domain3.com relay:[isp.mtabak.com]
>
> Postfix uses always the second entry.
>
> Is there a way to tell Postfix to use one and if the connection fails use
> the other, just like a DNS MX weight?

No. Use MX records, or hostnames that resolve to multiple IP addresses.

--
Viktor.

[Luigi Rosa]

Viktor Dukhovni wrote on 11/05/2015 19:39:

> This advice is bad. Any problems with RBLs manifest *after* the
> destination relay has accepted your mail. Therefore adding a
> failback does no good. All the mail goes to the primary anyway.

I know... But the IT guy of my customer asked for it.

Glad to hear that it is not possible without fiddling with MX.

My personal advice is "choose a better ISP", but you know... cost savings...


Thank you.

--


Ciao,
luigi

/
+--[Luigi Rosa]--
\

The world is coming to an end... SAVE YOUR BUFFERS!!!