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Email domain health monitoring

Know the day your email setup breaks.

SenderBeacon watches SPF, DKIM, DMARC, MX and your HTTPS certificate, and emails you in plain English when something fails or changes, before your mail starts landing in spam.

Free, instant, no signup. Read-only DNS lookups. We never email your domain.

Example alertfrom hello@trysenderbeacon.com
Action needed: SPF is failing on example.com

SPF needs 12 DNS lookups. The limit is 10, so receivers
return "permerror" and SPF fails.

What to do:
- Remove services you no longer send from, or replace an
  include with the ip4:/ip6: ranges it covers.

Why this breaks

Email authentication fails silently. Nobody gets an error. Mail just goes to spam.

A new tool adds a second SPF record. Two SPF records means SPF fails for every message you send.

A DNS move drops the DKIM key. Messages go out unsigned, and DMARC fails wherever SPF does not align.

Gmail, Yahoo and Microsoft now enforce. Bulk senders without SPF, DKIM and DMARC are filtered or rejected.

How it works

Set it up once. Hear from us only when it matters.

1. Add your domain

Type the domain you send from, plus your DKIM selector if you know it. We scan it straight away.

2. We check twice a day

Five checks every 12 hours. A failure must repeat before we alert, so one DNS blip will not page you.

3. Plain-English alerts

What broke, why it matters and the exact fix. Change alerts when a record is edited, recovery emails when it is fixed.

Free tools

Check one thing right now

Email domain health checkOne scan of the five records that decide whether your email is trusted.SPF record checkerPaste a domain to see its SPF record, how many of the 10 allowed DNS lookups it uses (counting nested includes), and what to fix..SPF “too many DNS lookups” checkerSPF allows 10 DNS lookups in total, including those inside nested includes.DMARC record checkerEnter a domain to read its DMARC record at _dmarc.<domain>, check it is valid, and see what the policy actually does to spoofed mail..DKIM record checkerEnter your domain and, if you know it, your DKIM selector.MX record lookupMX records tell the world which servers accept mail for your domain.SSL certificate expiry checkerEnter a domain to see whether its HTTPS certificate is trusted, who issued it, and how many days are left before it expires..SPF record generatorTick your senders, copy one valid record.DMARC record generatorPick a policy, copy the TXT record.

Setup checks for: Google Workspace, Microsoft 365, Zoho Mail, SendGrid, Mailgun, Amazon SES, Fastmail, Proton Mail

Pricing

Every check on every plan. Always under $20.

14-day free trial on one domain, no card. Cancel or switch plans yourself in the billing portal.

Common questions

Do I need a card for the trial?

No. The 14-day trial monitors one domain with no card. Pick a plan any time from your dashboard; checkout is handled by Stripe.

How do I cancel?

From the dashboard, click "Manage billing". That opens the Stripe customer portal, where you can cancel, switch plans, update your card or download invoices without contacting anyone. Cancelling stops renewal at the end of the period you paid for.

What happens when I hit my domain limit?

You cannot add more domains until you upgrade or remove one. Existing domains keep being monitored.

How often do you check?

Twice a day, plus an instant scan whenever you add a domain or click "Scan now". A failure has to show up on two scans in a row before we alert, so a one-off DNS blip does not wake you up.

Do you read my email or need access to my DNS?

No. We only read public DNS records and the public HTTPS certificate, the same data anyone on the internet can see. No logins, no API keys, no inbox access.