The gwhitelist script assists mail administrators in placing the google outbound SMTP servers on a Postfix postscreen whitelist.
The output format can be changed easily to suit other purposes.
It is presumed that the mail administrator already knows how to use Postfix's postscreen whitelisting facility.
The script generates a list of CIDR-formatted IP addresses from google's SPF records, and outputs the list to stdout in a format suitable for a postscreen CIDR lookup table.
Tested under OpenBSD 5.3, FreeBSD 9.1, and Debian GNU/Linux 6.0.6.
Download gwhitelist 1.1 (2KB)