How to fix a failed send

What to do when a campaign, workflow, test, or transactional send is rejected.

You got a send failure such as Message rejected, Email delivery failed, Workflow email send failed, or campaign send failed. The message never left, or the provider refused it.

What to change

Open the linked campaign, workflow, or Domains page from the notification.
Read the last sentence of the alert — it names the provider code.
Fix the matching cause:

Code / wording	Fix
MAIL FROM / `MailFromDomainNotVerifiedException`	How to fix MAIL FROM
Domain not verified / identity paused	How to verify a sending domain
Invalid from/to/subject/headers	How to fix an invalid email parameter
Configuration set missing / sending paused	How to fix sending infrastructure
Rate or daily quota	How to fix sending rate or daily quota
Internal error / “bug on our side”	Nothing on your DNS. Email [email protected] with the org slug and the technical detail.
Message rejected (generic)	Confirm the From address uses a verified custom domain, the recipient is not suppressed, and the campaign still renders. Then retry.

After DNS changes, verify the domain, then resend or resume the campaign/workflow.

Fallback already delivered through another domain? See How to fix a fallback-domain send.

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