DIAGNOSTIC PLAYBOOK
Copying a message can change DKIM verification results
Copying rendered email into a text editor can change line endings, encoding or MIME structure. A signature check needs the raw message bytes, so a reconstructed copy may fail even if the original verified.
HealthCheck Email editorial team · · Examples are illustrative
How to investigate
- Export the original message source or EML through the receiving provider's supported method.
- Avoid rich-text editors or tools that normalize line endings before verification.
- Compare your local result with the trusted receiver's recorded result and note any differences in the input.
What this looks like
ILLUSTRATIVE EXAMPLE
A copied HTML message loses MIME boundaries when pasted from its rendered view. The reconstructed body is not the body that was signed.
A mistake to avoid
Do not diagnose a sender outage using only a manually reconstructed message. Preserve the original before testing transformations.
Keep the result in context
Inspect the original raw message rather than a forwarded screenshot. Headers can contain private addresses, message identifiers and routing information, so redact a separate copy before sharing. Give the most weight to results added by your own trusted receiving infrastructure.
Take the next step
Use the related check to gather evidence, then compare it with the affected message or service. Keep the result and time with your notes so a later change can be distinguished from the original problem.
Sources and further reading
The protocol references below explain the underlying behavior. Your sending or DNS provider supplies the account-specific settings for its service.