The campaign no one knew was failing
A Delivery Center customer saw a sudden drop in SPF pass rates in their DMARC reports. Delivery Center matched the unfamiliar sending IPs to Mailchimp. One department had started sending campaigns through Mailchimp without telling IT, so Mailchimp wasn't in the SPF record and much of that mail was being rejected. The team had noticed poor open rates but never connected them to authentication.
Without monitoring, the problem would have stayed hidden until the failures damaged the sender's reputation.
What breaks DMARC after setup
| Cause | What you'll see | How Delivery Center helps |
|---|
| A new tool nobody added to SPF | SPF failures from a source you don't recognize | Matches sending IPs to known third-party services, so you know who to add |
| A vendor changes its IPs or SPF include | A sender that used to pass starts failing SPF | Pass rates by sender show exactly which vendor changed |
| More than 10 SPF lookups | SPF returns an error, and most receivers fail it for every sender | SPF checks flag the lookup count; SPF Flattening on Plus keeps you under 10 |
| DKIM key or selector rotation | DKIM failures after a DNS change | DKIM pass rates by sender and selector |
| A vendor signs with its own domain | Passes DKIM, but fails DKIM alignment | Alignment shown for each sender, so you know who relies on SPF alone |
| Forwarding and mailing lists | Small, steady SPF and DKIM failures | Unaligned domains like gmail.com show where forwarding, not misconfiguration, is the cause |
| Spoofing | Mail volume "from" your domain jumps, from unknown IPs | Unknown and unauthorized senders flagged; enforcement stops them |
Some failures are normal: forwarding changes messages and breaks DKIM signatures. Watch for changes, not perfection.
How Delivery Center keeps watch
1
Collect every report
Point your DMARC record's reporting address at MxToolbox. Reports from Google, Microsoft, Yahoo! and 500+ other inbox providers land in one place.
2
Name every sender
Each sending IP is matched to a known service, so you see Mailchimp or Salesforce, not a string of IP addresses.
3
Catch changes early
SPF, DKIM and DMARC pass rates by sender, alerts for new or failing senders, and step-by-step fixes.
Monitoring is also what makes enforcement safe. Compliance at p=none is the short-term goal; enforcement (quarantine, then reject) is the ultimate goal, protecting your brand, sending reputation and business from BEC. But at p=reject, a sender that falls out of SPF doesn't land in spam. Its mail is rejected. Learn about DMARC enforcement →
Built for the way your team sends
Email Marketers
Find out that a new tool or campaign is failing authentication before poor open rates tell you, and keep every ESP passing.
DMARC Adopters
See pass rates by sender and selector, move to quarantine and reject with confidence, and catch regressions before enforcement blocks your own mail.
IT Email Administrators
Spot unapproved senders, vendor IP changes and key rotations that break SPF or DKIM, and fix them before users report bounces.
Start Monitoring
Passing DMARC, but still in spam?
Authentication is only the first layer. Reputation, content and complaints decide between the inbox and the spam folder.
Find out why email goes to spam →
20+ years in email deliverability
42K+Domains trust MxToolbox
500+DMARC-reporting inbox providers
114M+DMARC digests processed annually
MillionsMessages processed hourly
Part of Delivery Center
DMARC monitoring is one piece of a full email reputation toolkit. Paid Delivery Center plans also include:
DMARC Compliance
Find every sender and meet Google, Yahoo! and Microsoft sender rules.
Learn more →
DMARC Enforcement
Move safely to quarantine and reject and stop spoofing of your domain.
Learn more →
SPF Flattening (Plus)
Stay under SPF's 10-lookup limit as vendors add includes.
Learn more →
See everything in Delivery Center →