Secure email — intermittent send failures (Paubox)

Update: The automatic retry mechanism is now live in production. Outbound secure emails rejected by the ongoing validation rollout at Paubox are retried automatically, so the send failures should no longer be visible in day-to-day use. We are monitoring delivery closely.
This is a temporary mitigation. The permanent fix: aligning our sending-domain configuration with Paubox's new validation model, has not been applied yet and is still in progress. We expect to complete it within the next couple of days.

What's happening: Paubox, our secure email delivery provider, is rolling out a stricter sending-domain validation model across their infrastructure as a security enhancement. Under the new logic, each API key must be tied to a single verified sending domain. Because the rollout is staged across their servers, some outbound messages are rejected while identical messages sent moments earlier succeed. Affected messages appear in the Sent tab with a Failed (Secure) status and were not delivered.

No data was lost and nothing was sent insecurely. Inbound email, SMS, calls, and the rest of Comm Center are unaffected.

What we've done: We have implemented automatic retry for secure email on our side and will deploy it today. Once live, rejected messages will be retried automatically, which should resolve the failures you may have been seeing in day-to-day use. This is a temporary mitigation while we complete the underlying sending-domain configuration with Paubox; we expect a permanent fix within the next couple of days.

We are continuing to investigate this issue.

Some outbound secure emails are being rejected by Paubox, our secure email delivery provider, and appear in the Sent tab with a Failed (Secure) status. The rejection returns a "400 Bad Request — From domain is not an approved sending domain for your account" error. Messages with that status were not delivered. No data was lost and nothing was sent insecurely.
Inbound email, SMS, calls, and the rest of Comm Center are unaffected.

Workaround: resending the message usually succeeds. We recommend checking your Sent tab for Failed (Secure) messages and retrying anything time-sensitive.

We are working directly with Paubox to confirm the root cause and restore normal delivery.