Free tools
Free email deliverability tools
The DNS layer of email, checked properly: every include resolved, every CNAME followed, every verdict in plain words with the fix. No signup, nothing stored, and results 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.
DKIM checker
Test a DKIM key by selector, or probe 15 common selectors at once.
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.
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.
Private beta
Built by people who obsess over this layer
SendHeron is lifecycle email automation for SaaS, in private beta. If you want your sequences and transactional mail running on top of authentication done right, join the list.