Postfix: Setup DNS spf

Caranya:

Name/Host/Alias: Enter @ or leave it blank. Your other DNS records might indicate which entry is correct.
Time to Live (TTL): Enter 3600 or leave the default.
Value/Answer/Destination: Enter v=spf1 include:_spf.google.com ~all

Misalnya:

onnocenter.or.id.       IN      TXT     "v=spf1 mx include:_spf.google.com ~all"

Example 2 Allow mail from a specific host:

v=spf1 a:mail.example.com -all

The v=spf1 tag is required and has to be the first tag.

The last tag, -all, indicates that mail from your domain should only come from servers identified in the SPF string. Anything coming from any other source is forging your domain. An alternative is ~all, indicating the same thing but also indicating that mail servers should accept the message and flag it as forged instead of rejecting it outright. -all makes it harder for spammers to forge your domain successfully; it is the recommended setting. ~all reduces the chances of email getting lost because an incorrect mail server was used to send mail. ~all can be used if you don’t want to take chances.

Referensi

• https://support.google.com/a/answer/33786?hl=en