Monitor Your Sending Domains: SPF, DKIM and DMARC Alerts
To monitor your sending domains, check each one every day for MX, SPF (including the 10-DNS-lookup limit), DKIM, DMARC and public blocklists, and get told when something changes, with the fix. SimpleVerifier Monitoring does exactly that for the domains you add. Changes go on a per-domain timeline and show as alerts on the Monitoring page in your dashboard. Email alerts are not available yet, so check the page before big sends.
Why domains break without anyone touching them
Most broken authentication is not a typo on day one. It is drift:
- SPF goes over 10 lookups. Someone adds a new tool's
include:and SPF now fails for every message. Nothing visibly breaks until replies dry up. - A DKIM key disappears. A DNS migration or a tool switch drops the selector your sender signs with.
- DMARC gets duplicated. Two DMARC records mean receivers treat it as no valid record.
- MX goes missing. A domain bought for cold email never got mail servers, so replies bounce.
With 10 or 20 secondary domains, nobody re-checks them all by hand.
What gets checked
| Check | What it looks for |
|---|---|
| MX | The domain has mail servers, so replies arrive. A null MX or a missing record is flagged. |
| SPF | One valid SPF record within the 10-DNS-lookup limit. |
| DKIM | A signing key on about 80 common selectors plus the one you give us, with key length and test mode checked. |
| DMARC | A single valid record and its policy. p=none is shown as something to improve; a missing or broken record as something to fix. |
| Blocklists | IPs your domain controls (single IPs in SPF, a self-hosted MX) on Barracuda, SpamCop, PSBL and Mailspike; the domain on URIBL and NordSpam. |
Spamhaus is not queried, because its free service is for non-commercial use. Check it on Spamhaus's own site.
All of this is DNS lookups. Nothing is sent to or from your domain.
Set it up
- Open Monitoring in the dashboard and add each sending domain.
- If your sending tool uses a custom DKIM selector, add it so it is checked along with the common ones.
- Read the first day's results and fix anything marked red. Each item says what to change.
- Before any large send, open the timeline and check nothing changed since your last look.
You can try the same checks once on any domain, with no account, using the free email domain health checker.
The optional 30-day list re-check
Monitoring can also re-check a saved list every 30 days, so addresses that went bad since you verified them are caught. It is off until you turn it on for a list, and the page shows how many addresses each run checks first. A run is an ordinary verification on your plan, only valid and risky addresses are kept, and turning it off deletes the saved addresses.
Plans
Monitoring is included in paid plans: 1 domain on Starter, 3 on Growth, 10 on Pro, 25 on Business and 100 on Agency. Free checks and trials do not include it. Prices are on pricing.
Run 100 free checks on a list from one of those domains, so you know the list is as clean as the DNS.
Related reading
- DMARC from none to reject for tightening the policy safely.
- Cold email domain setup for the records each new domain needs.
- Gmail and Yahoo bulk sender requirements for what the big providers now enforce.
Common questions
What should I monitor on a cold email sending domain?
MX records, so replies arrive; one valid SPF record within the 10-DNS-lookup limit; a DKIM key on the selector your sending tool uses; a single valid DMARC record and its policy; and whether the IPs or the domain appear on public blocklists.
How often does SimpleVerifier check my domains?
Once a day per domain. When a result changes from the day before, the change goes on the domain's timeline with what changed and the exact fix.
Will I get an email when SPF or DMARC breaks?
Not yet. Alerts show on the Monitoring page in the dashboard, with the fix. Email alerts are not available yet.
Does Monitoring check Spamhaus?
No. Spamhaus's free service is for non-commercial use, so it is not queried. Monitoring checks Barracuda, SpamCop, PSBL and Mailspike for IPs your domain controls, and URIBL and NordSpam for the domain. Check Spamhaus on its own site.
How many domains can I monitor?
It depends on the plan: 1 on Starter, 3 on Growth, 10 on Pro, 25 on Business and 100 on Agency. Free checks and trials do not include Monitoring.
Check your list before you send
Real mailbox checks over SMTP, and nothing is sent to the address. Sign in with Google and your first 100 email checks are free, no card. Plans for bigger lists are on the pricing page.