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.
