SPF (Sender Policy Framework) records are used to authenticate email messages and prevent them from being marked as spam. To create SPF records for your Google Apps domain in BIND or djbdns, you’ll need to add a text (TXT) record to your domain’s DNS configuration.
Here’s an example SPF record for a Google Apps domain using BIND:
example.com. IN TXT "v=spf1 include:_spf.google.com ~all"
In this example, the v=spf1 part of the record specifies that this is an SPF version 1 record. The include:_spf.google.com part allows Google’s mail servers to send email on behalf of your domain. The ~all part specifies a “soft fail” mechanism, meaning that any emails that do not come from a source listed in the SPF record will not be rejected outright, but may be marked as potentially spam.
For djbdns, the process is similar, but the syntax is different. Here’s an example SPF record for a Google Apps domain using djbdns:
example.com:v=spf1\ include:_spf.google.com\ ~all
Note the use of backslashes to escape the spaces in the record.
Once you’ve added the SPF record to your domain’s DNS configuration, it may take some time for the changes to propagate throughout the Internet. After that, email messages sent from your Google Apps domain should be properly authenticated and less likely to be marked as spam.