You got **Sustained delivery delays are above 10% of sent mail**. Receiving servers accepted the message later (or greylisted / deferred it). This measures **delivery delay**, not inbox vs spam.

## What to change

Delays usually mean the far side is throttling you or retrying. Check, in order:

1. **Volume spike** — a sudden list blast after quiet weeks. Slow the send; don’t retry the same delayed cohort immediately.
2. **List quality** — high bounces/complaints in the same windows. Fix those first ([bounce](/docs/deliverability/how-to-lower-bounce-rate), [complaints](/docs/deliverability/how-to-lower-complaint-rate)).
3. **Authentication** — open domain alerts on **Settings → Deliverability**. Failed DKIM/SPF/DMARC makes deferrals more likely.
4. **Content** — run the [content checker](/docs/features/content-deliverability) on the campaign that was in-flight.
5. **Dedicated IP warmup** — if you use a dedicated IP, see [How to fix a dedicated IP](/docs/deliverability/how-to-fix-dedicated-ip).

You cannot force Gmail or Microsoft to stop greylisting. You can stop looking like a bursty or unauthenticated sender.

## After it recovers

The alert resolves when consecutive adequate windows stay below 10% delayed / sent.

## Related

- [Sender Health](/docs/features/sender-health)
- [Campaign Delivery Score](/docs/features/deliverability-score)