DIAGNOSTIC PLAYBOOK
A recipient domain typo causes delivery failure
A typo after the at sign can route mail to an unintended domain or no usable mail service. Check the actual envelope recipient before modifying your own authentication records.
HealthCheck Email editorial team · · Examples are illustrative
How to investigate
- Compare the address in your application with the source supplied by the recipient.
- Inspect the destination domain's DNS and the exact bounce response.
- Confirm corrections with the contact rather than guessing and retry only to the verified address.
What this looks like
ILLUSTRATIVE EXAMPLE
A signup stores example.con instead of example.com. The resulting delivery failure is unrelated to the sender's DKIM selector.
A mistake to avoid
Do not automatically rewrite ambiguous addresses to a popular domain. A guessed correction can disclose mail to a different recipient.
Keep the result in context
A successful handoff, a delivered event and an inbox placement are different observations. Record the receiving provider, send time, SMTP response and affected stream before comparing results. DNS fixes address authentication or routing; they cannot establish consent or guarantee placement.
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.