Free tools
Free email deliverability tools
Email authentication, checked properly: every include resolved, every CNAME followed, every header read, every verdict in plain words with the fix. No signup and nothing stored, and the checkers run live, so a shared link always shows the current state.
DMARC checker
Read any domain's DMARC record: policy, reports, and what to fix.
SPF checker
Resolve the whole SPF tree and count lookups against the limit of 10.
SPF record generator
Build one SPF record from your senders, with every lookup counted.
DKIM checker
Test a DKIM key by selector, or probe 15 common selectors at once.
DKIM record generator
Make a DKIM key pair in your browser and copy the record to publish.
DMARC record generator
Build the exact DMARC TXT value and know exactly where to publish it.
Email deliverability test
MX, SPF, DKIM and DMARC in one pass, with a prioritized fix list.
Email header analyzer
Trace an email's route and delays, and read its SPF, DKIM and DMARC.
These exist because we run this layer for a living: SendHeron is lifecycle email automation, and authentication is the floor it stands on. The checkers implement the actual RFC rules, including the ones most tools skip, like the recursive 10 lookup limit and CNAME-published DKIM keys, and every failure verdict tells you what to do about it.
Free trial
Built by people who obsess over this layer
SendHeron is lifecycle email automation for SaaS. If you want your sequences and transactional mail running on top of authentication done right, start a trial.
7-day free trial. Pick a plan, add a card, cancel before the trial ends and you won't be charged. 1,000 contacts and 5,000 sends during the trial.