Postfix is not able to connect to the 100.100.100.100 address on the 3G network. The real IP address is on the non-routable 10.* subnet.
I shall however do some testing tomorrow and send a "postconf -n". Thanks for the help so far. /MB ________________________________ Mark Baxter OnDemand Administrator, Visma Proceedo AB Switchboard : +46 8 522 930 30 - Direct : +46 8 522 930 60 - Mobile : +46 73 978 92 60 - Fax : +46 8 58 88 48 29 ________________________________ -----Original Message----- From: owner-postfix-us...@postfix.org [mailto:owner-postfix-us...@postfix.org] On Behalf Of Noel Jones Sent: den 28 september 2009 18:00 To: postfix-users@postfix.org Subject: Re: Failover from one remote SMTP server to another On 9/28/2009 10:23 AM, Mark Baxter wrote: > Hi, > > I am currently using Postfix to relay email to a remote SMTP server run > by the company I work in (we use it for sending Nagios notifications). > As this network connection is occasionally not so reliable we would like > to use a 3G connection as a backup network connection and doing so would > require using the mobile company's SMTP server. > > 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 = 100.100.100.100 > > smtp_fallback_relay = smtp.3g.com > > 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. > > Now, the network failover is working fine (this is on Ubuntu 9.04). No > problems there at all. My problem is that Postfix is still trying to > relay to 100.100.100.100. I tested this by pulling out the network > cable. The ethernet link was down and the machine was using the 3G network. Postfix will always attempt to connect to $relayhost, and will only use smtp_fallback_relay if it can't connect to the relayhost at all. 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. If you need more help, please show "postconf -n" output and logging demonstrating the problem. -- Noel Jones
