SPF is a DNS TXT record that lists which mail servers are allowed to send email on behalf of your domain. Receiving servers check this list — if an email claims to be from you but comes from a server not on the list, it's treated as suspicious.
Missing or misconfigured SPF is one of the most common reasons legitimate email lands in spam. It's also one of the first things spammers skip — so a strong SPF record is a baseline trust signal.
Too many DNS lookups (SPF has a 10-lookup limit), multiple SPF records on one domain (only one is valid), forgetting to update it when switching ESPs.
Run a free, instant audit of SPF and every other authentication record on any domain.
Run a Free SPF CheckWhen a competitor switches ESPs, their SPF record usually changes within days — one of the clearest "they just migrated" signals CompetitorInbox surfaces automatically.