Deliverability starts with DNS
Gmail and Yahoo (since February 2024) and Outlook.com (since May 2025) require SPF, DKIM and DMARC from anyone sending around 5,000 or more messages a day. These tools help you get there without guesswork.
Free · no sign-up
Free e-mail deliverability & DNS tools
Everything you need to authenticate your domain, troubleshoot delivery and keep your lists clean — free, without an account. The generators and analyzers run entirely in your browser.
Validate addresses
Authenticate your domain (SPF, DKIM, DMARC)
SPF, DKIM & DMARC checker
Grade a domain’s e-mail authentication against the Gmail, Yahoo and Outlook bulk-sender rules.
Open tool →DMARC record generator
Build a valid DMARC TXT record step by step, with a safe none → quarantine → reject rollout.
Open tool → 🔒SPF record generator
Pick your sending services and get one correct SPF record, with a live count of DNS lookups.
Open tool → 🔒DKIM checker
Look up the DKIM public key for a domain and selector, and check its type and length.
Open tool →Analyze messages and reports
DNS and reputation
DNS lookup
Query A, AAAA, MX, TXT, NS, CNAME and other DNS records of any domain.
Open tool →MX lookup
List the mail servers of a domain, in priority order, with their IP addresses.
Open tool →Blacklist checker
Check whether a mail server IP or domain is listed on the major DNS blocklists.
Open tool →Why these tools are free
Private by design
The SPF and DMARC generators, the header analyzer and the DMARC report analyzer never send your data anywhere — the work happens in your browser. Tools that query DNS receive only the domain or IP you enter.
The other half: your list
Authentication tells mailbox providers who you are; list quality decides how they treat you. When you are ready, validate your lists in bulk with a free AT Valid account.
Frequently asked questions
Are these tools really free?
Yes. All tools on this page are free and need no account. Tools that query DNS may have a daily limit per visitor to prevent abuse; the generators and analyzers have no limit at all.
Do you store the domains, headers or reports I check?
The SPF and DMARC generators, the header analyzer and the DMARC report analyzer run 100% in your browser: nothing you type, paste or open is uploaded. Tools that query DNS send only the domain or IP you enter.
Where should I start?
Run the SPF, DKIM & DMARC checker on your sending domain. It grades your setup and lists what to fix; then use the SPF and DMARC generators to build the missing records.
What do Gmail, Yahoo and Outlook require from bulk senders?
SPF and DKIM, a DMARC record (p=none at least) with the From domain aligned to SPF or DKIM, one-click unsubscribe for marketing mail, valid reverse DNS, TLS, and a spam-complaint rate under 0.3%.
What is the difference between e-mail validation and domain authentication?
Authentication (SPF, DKIM, DMARC) proves that mail from your domain is really yours. Validation checks whether the addresses you send to exist and are safe. You need both: one protects your domain, the other protects your reputation from bounces.
Can I use these tools for client domains?
Yes. Agencies and IT teams use them to audit and fix client domains. For recurring work at scale — bulk validation, API, integrations — create a free account with 200 credits.
Ready to clean your list?
A free account gives you 200 credits to validate e-mail lists in bulk, through the REST API or in real time on your forms.
Create free account — 200 creditsNo credit card. Credits never expire.