JoshData/mailinabox — pull request #70 by mkropat (2014-06-08 22:50:03+00:00)
Title: Support dual-stack IPv4/IPv6 mail servers

Addresses #3

Added support by adding parallel code wherever `$PUBLIC_IP` was used.
Providing an IPv6 address is completely optional.

Playing around on my IPv6-enabled mail server revealed that — before
this change — mailinabox might try to use an IPv6 address as the value
for `$PUBLIC_IP`, which wouldn't work out well.