Do I need SPF, and how to set it up

domain-name-systemmx-recordspf

I've read that SPF is a way to ensure that spam sent in my name is evidently fake, and I'd like to use that. How do I set up SPF? Or is it already in effect? I have two domains hosted on Dreamhost.com, and I use Google Apps to read mail on both domains (separately).

I have used this tool to check if SPF is present for my domains. One domain has SPF, one doesn't.

But it gets more complicated than that:

A) The domain with SPF uses Dreamhost as MX. Mail accounts on this domain are set up to forward to specific Google Apps accounts.

  • Is my SPF ignored when sending mail from Google Apps?

B) The domain without SPF uses Google as MX. I want to add SPF to this domain.

  • Can I add SPF under this domain's DNS records, or should this be done at Google (outside my control)?

C) Further, the users are in several countries using several ISP's. Some don't use the Gmail web interface but rather a mail client (Thunderbird, Outlook). So it's really difficult to say which IP addresses are "ours". This goes for both domains.

  • What IP addresses can/should/must I (not?) specify in my SPF records?

Best Answer

SPF doesn't care about clients, it is about the question "which server is allowed to send mails coming from my domain?"

Assuming you own the domain example.org:

  • A) It's not important where you send your mails from. It's important that your mailserver has SPF records that match your mailserver.
  • B) Google.
  • C) It's typical to trust the A and MX record resolving to that domain, so: v=spf1 a mx -all
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