What is SPF flattening? A Plain-English Guide
SPF flattening replaces include statements with their resolved IPs to stay under SPF's 10-DNS-lookup limit, preventing permerror failures for senders with many services.
Why it matters for deliverability
Understanding SPF flattening is part of fixing 'too many DNS lookups'. Get it right and more of your mail reaches the inbox; get it wrong and even legitimate mail can be filtered.
Related
How Rainmail helps
Rainmail sends from your own domain on a dedicated, isolated IP with SPF, DKIM, DMARC, reverse-DNS and managed warm-up handled for you, plus an AI that watches your list health and deliverability — and it welcomes the senders Amazon SES, SendGrid and Mailchimp reject, from $8. Run the free 10-second checker or see plans.