Spam Resource: Ask Al: SPF -all or ~all?

Al Iverson just posted another brilliant write-up on Spam Resource:

Hey, Al! I was wondering if you could provide some guidance about SPF record format. Is it better to list the exact IP(s) in the SPF record? How about using the SPF dash (-all), or tilde (~all)? Which way is more common and better for deliverability? SPF aka Sender Policy Framework is a form of email authentication. It’s basically just a DNS record that you configure for your domain, and that DNS record usually just contains a list of the IP addresses of your mail servers (or somebody else’s mail servers that are allowed to send mail on behalf of your domain). Wikipedia’s the place to start if you want to dive into what SPF is in great detail. If you’re reading on past this point, I’m going to assume that you know what an SPF record looks like.When you create an SPF record, the last bit of it ends in…

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