Exim: IPv6 socket creation failed: Address family not supported by protocol

If your emails are not able to leave the box and you're getting errors like this

2013-01-25 01:31:27 2TyWGU-0004ex-Hp IPv6 socket creation failed: Address family not supported by protocol
2013-01-25 01:31:27 2TyWGU-0004ex-Hp gmail-smtp-in.l.google.com [2a00:1450:4010:c03::1a] Address family not supported by protocol
2013-02-06 03:35:07 1U31bI-0005f3-Km ASPMX.L.GOOGLE.com [2607:f8b0:4001:c02::1b] Network is unreachable
2013-02-14 11:22:32 1U6t2I-0004Ne-OW ASPMX.L.GOOGLE.COM [2607:f8b0:4001:c02::1a] Connection timed out

it means that your network device has IPv6 enabled, but your network itself doesn't support it.

The simple solution is to tell exim not to use IPv6 by adding the following to the top of your /etc/exim.conf

disable_ipv6=true