Are there risks associated with SPF flattening?

Your ESP suggested SPF flattening to solve the 10-lookup limit, and honestly that's a reasonable suggestion. But flattening comes with its own set of problems, and it's worth understanding them before you commit.

Quick recap if you need it: SPF flattening means you resolve all those include: references in your SPF record down to their actual IP addresses and list those IPs directly. No more recursive lookups, no more hitting the limit. Sounds clean, right? Here's where it gets messy.

The stale IP problem is the biggest one. When you flatten your record, you're taking a snapshot of your sending providers' IP addresses at that exact moment. Providers like SendGrid, Mailchimp, or Postmark rotate and add IPs all the time, often without telling you. The day they add a new IP range, your flattened record is out of date. Emails sent from those new IPs will fail SPF, and you probably won't notice until someone's mail bounces or starts hitting spam.

Manual flattening is basically unsustainable. To keep it accurate, you'd need to monitor every provider's IP changes, re-flatten whenever something shifts, and push the DNS update before the change takes effect. That's a full-time job for something that should be set-and-forget. (And let's be honest, nobody actually does this consistently.)

You can also hit TXT record length limits. SPF records that expand into dozens or hundreds of IP addresses can bump into the 255-character string limit per chunk, or the overall record length limit. It's fixable with careful formatting, but it adds yet another thing to manage. There's more on TXT record limits if you want the full picture.

And there's a readability issue. A record full of raw IPs like 203.0.113.5 and 198.51.100.44 tells you nothing about which service they belong to. If something breaks six months from now, good luck auditing which IP belongs to which provider.

The better path for most senders is an automated flattening service. These tools monitor your providers' IP ranges in real time and update your DNS record automatically when things change. You get the lookup-count benefit without the stale-data risk. A few providers offer this as part of their SPF management tooling.

But if you're not sure whether flattening is even necessary for your setup, check your current SPF record with our free SPF checker. It'll tell you exactly how many lookups you're burning and whether you're close to the limit. Or if you'd rather talk it through, our SOS hotline is free.