On Mon, Sep 28, 2009 at 11:00:15AM -0500, Noel Jones wrote:
>> After searching online and reading a lot it seemed to me that, assuming
>> that the company?s SMTP server is 100.100.100.100 (for one reason or
>> another we use the IP address rather than FQDN) and the 3G operator?s
>> SMTP server is smtp.3g.com, what I needed was this in the Postfix
>> configuration:
>>
>> relayhost = 192.0.2.1
Change that to include the required "[]" around the bare IP:
relayhost = [192.0.2.1]
>> smtp_fallback_relay = smtp.3g.com
Fine.
>> The idea being that when the link to 100.100.100.100 is down (as in that
>> network connection is down) the machine failsover its network
>> connectivity to the 3G one and uses smtp.3g.com.
>
> Postfix will always attempt to connect to $relayhost,
correct.
> and will only use
> smtp_fallback_relay if it can't connect to the relayhost at all.
No, Postfix (from 2.1 and later IIRC) will also use the fallback relay
after a 4XX failure in a delivery attempt via the primary nexthop,
unless the current host is a back-up MX for the destination domain.
> If postfix is able to connect to 100.100.100.100 via the 3G connection, the
> fallback settings will never be used - even if the actual mail transfer
> fails.
This is not accurate.
> If you need more help, please show "postconf -n" output and logging
> demonstrating the problem.
Logging would be very useful.
--
Viktor.
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