Sender Policy Framework (SPF) is a DNS-based authorisation check. It allows a receiving mail system to compare the server delivering a message with the sending services permitted by the relevant domain.
SPF is only one part of sender authentication. For reliable alignment and protection against spoofing it should normally be used alongside DKIM signing and DMARC.
Include AuthSMTP in your existing record
If you already have an SPF record, add the following mechanism before its final all mechanism:
include:authsmtp.comDo not publish a second SPF record for AuthSMTP. A domain should have one SPF policy that describes every legitimate source of its outgoing email, including web applications, business mail platforms and other providers.
Check the whole sending estate
Before changing DNS, list every system that sends using your domain. Removing an existing provider from SPF can cause otherwise legitimate messages to fail authentication. Equally, leaving retired services authorised increases unnecessary exposure.
- Keep the record as short and understandable as practical.
- Use TXT records; do not use the retired SPF DNS record type.
- Stay within SPF's DNS-lookup limit.
- Allow time for DNS caches to expire after a change.
- Test mail through the normal production route after publishing.
Where to get the exact setup help
Our detailed AuthSMTP SPF setup instructions cover record syntax, examples and common errors. The AuthSMTP Control Panel can also show the SPF record currently visible for your domain.
Add include:authsmtp.com to your existing SPF record, then verify the complete record rather than publishing a separate one.
Review the existing TXT record with whoever manages your DNS, add AuthSMTP to that record, and verify that all other genuine sending sources remain authorised.