I’ve been fine-tuning the configuration of my servers. Some notes from my experiences. One of my VPS’es runs a kernel compiled by the server company. This kernel has disabled IPv6 support. (Why are there still server companies that don’t offer IPv6 in the year 2016? I mean *click*) Anyways… running a kernel without IPv6 makes many daemons throw warnings. I am in particular looking at my mail configuration:

postfix[565]: warning: inet_protocols: disabling IPv6 name/address support: Address family not supported by protocol

To make all these warning gone (they pollute the logs) edit the /etc/postfix/main.cf

inet_protocols = all

with 

inet_protocols = ipv4

When I want to use greylisting on my server, using postgrey. Well… postgrey… will fail when it’s unable to bind to an IPv6 socket. And looking for a configuration file to configure the listning socket??? Where the hell is it. It seems, on a Ubuntu server, we’ll have to look in /etc/default/postgrey. This file specifies the startup parameters when postgrey is started using postgrey service start.

The default value is:

POSTGREY_OPTS="--inet=10023"

This will try to bind a socket to both IPv4 and IPv6 localhost. In order to make it only bind to IPv4 localhost, change it into

POSTGREY_OPTS="--inet=127.0.0.1:10023"

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