DIAGNOSTIC PLAYBOOK
Temporary deferrals after a sending-volume spike
A volume spike can coincide with temporary deferrals, but the response text and provider context determine what to investigate. Separate rate-related replies from unrelated routing or authentication failures.
HealthCheck Email editorial team · · Examples are illustrative
How to investigate
- Group temporary replies by receiving provider, enhanced code and diagnostic wording.
- Compare volume and concurrency with the previous normal sending pattern.
- Follow the provider's guidance, preserve queue retries and avoid multiplying duplicate submissions.
What this looks like
ILLUSTRATIVE EXAMPLE
A campaign introduces several times the normal concurrent connections. One provider begins deferring while other destinations continue accepting mail.
A mistake to avoid
Reducing rate can be appropriate, but it does not repair a genuine authentication failure or establish permission to email the recipients.
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.