Why is Mailchimp Transactional (Mandrill) not sending my emails?
The Mailchimp Transactional (Mandrill) help pages give 3 common reasons. The first to rule out: If your sending domain is not verified, or its DMARC or DKIM records are missing or wrong, Mailchimp Transactional does not send from it.
Is it broken, or just quiet?
A number can fall because fewer people came, or because something stopped counting them. Below are the causes the Mailchimp Transactional (Mandrill) help pages give, and how to check each one yourself.
What causes it?
If your sending domain is not verified, or its DMARC or DKIM records are missing or wrong, Mailchimp Transactional does not send from it.
In the Mailchimp Transactional (Mandrill) help:
Mailchimp Transactional won’t send any email from unverified domains or domains without a valid DMARC policy and DKIM records.
Authentication and Delivery, read 2026-11-12.Emails rejected as unsigned point to a sending domain that is not fully set up, so the account cannot send from it.
In the Mailchimp Transactional (Mandrill) help:
A message that is rejected as unsigned indicates that the sending domain hasn’t been properly set up, and that your account is unable to authenticate and send email from that domain.
Authentication and Delivery, read 2026-11-12.If an app is using a test key, its emails are not really sent, which can happen after a settings change.
In the Mailchimp Transactional (Mandrill) help:
No emails are actually sent when you use a test API key for sending.
Fundamentals, read 2026-11-12.
How do I check it myself?
Check that every domain you send from is verified.
In the Mailchimp Transactional (Mandrill) help:
Domain verification is required to configure a sending domain.
Authentication and Delivery, read 2026-11-12.Confirm the domain has its DMARC and DKIM records and verified ownership.
In the Mailchimp Transactional (Mandrill) help:
You’ll need to add DMARC and a DKIM record, and verify ownership of your sending domains before you can send email through your account.
Authentication and Delivery, read 2026-11-12.Check which API key your app uses, since test mode emails are not sent.
In the Mailchimp Transactional (Mandrill) help:
Emails sent in test mode are specifically designed not to send, and won’t affect your account reputation.
Fundamentals, read 2026-11-12.
How would I know the day it starts?
- Feder reads your emails sent and your unique clicks from Mailchimp Transactional (Mandrill) each day and compares each day with your own history.
- It tells you when emails sent go quiet or move outside their usual range.
Some numbers are too quiet to judge daily, such as a form filled in a few times a week. Until there is enough of your own history to judge a change, Feder says it is still learning and scores nothing, rather than guessing.
See what Feder reads from Mandrill, which feeds Reach. Feder only reads. It never changes anything in Mandrill.
What else goes wrong with these numbers?
- Why did my Mailchimp Transactional (Mandrill) emails sent drop?Mailchimp Transactional (Mandrill)
- Why do my Mailchimp Transactional (Mandrill) unique clicks look wrong?Mailchimp Transactional (Mandrill)
- Why did Google Analytics stop collecting data?Google Analytics
- Why aren't my key events showing in Google Analytics?Google Analytics
- Why does Google Analytics show (not set)?Google Analytics
See every question.
Where do these answers come from?
Every cause and check on this page comes from the Mailchimp Transactional (Mandrill) help pages, quoted above with the date we read them. Last reviewed 2026-11-12. We read them again by 2027-11-12. If one changes, this page changes or comes down.