How to Verify and Respond to M365 Email Throttling

This article explains how to determine whether email delivery delays are due to a temporary service issue (throttling) and what to do to verify and respond.

What causes these temporary delivery delays

• Microsoft 365 (M365) can limit the number of concurrent connections to Paubox servers, which results in throttling.
• Throttling can produce "delivery failed temporarily" errors until Microsoft accepts the email into their servers.
• Throttled messages may later show as delivered once accepted.

How to verify if the issue is a temporary service throttling event

1. Check the Paubox system status page: https://status.paubox.com/ for current delays or incidents.
2. Subscribe to updates on the status page to receive automatic notifications about ongoing issues.
3. Review message delivery reports; messages that initially failed temporarily may later show as delivered.

What Paubox does during a throttling event

• Paubox monitors email flow and makes adjustments where possible to reduce impact.
• Mitigations or configuration changes may be implemented by the Paubox team (examples include changes rolled out at specific times to address throttling).

Troubleshooting steps for administrators

1. Confirm current incident status on the Paubox status page.
2. Monitor delivery logs for repeated temporary failures and subsequent deliveries.
3. If the system status indicates no incident but failures persist, contact Paubox support for investigation.

Delivery delays described in these cases are attributed to temporary throttling by M365 limiting connections, causing transient "delivery failed temporarily" errors that can resolve once Microsoft accepts the messages. Use the Paubox status page and delivery logs to verify and subscribe for updates.