Email authentication tools
Check any domain's SPF, DKIM and DMARC against what the RFCs actually require. No account, no limits worth mentioning, and every result explains what the problem is rather than just flagging it.
SPF record checker
Checks the record exists, counts the DNS lookups against the limit of ten, flags malformed mechanisms, and tells you what the trailing policy actually does.
Open the toolDMARC record checker
Reads the policy at _dmarc.yourdomain.com and explains what it actually enforces — including whether you are collecting the reports that make DMARC useful.
Open the toolDKIM record checker
Looks up selector._domainkey.yourdomain.com, follows the CNAME if your provider manages the key, and checks the key is present, long enough, and not in test mode.
Open the toolEmail domain checker
Runs every check at once. Use this one if you are not sure what is wrong — it looks at SPF, DMARC and your mail servers together, which is how a receiving server sees you.
Open the toolNew to any of this? SPF, DKIM and DMARC explained covers what each one does and why you need all three.