Message Delivery Triage in Sendblue
Last updated: April 12, 2026
Last Updated: April 12, 2026
Customer-Facing Guide
Start Here
If your messages are failing and you are not sure why, start with this guide. The most common causes are: request/formatting issues, using the wrong sending number, opt-outs, sending limits, or line-health problems.
The 5 Buckets to Check First
| Bucket | What it usually looks like | Best next step |
|---|---|---|
| Formatting / validation | Messages fail immediately because required fields or phone formatting are wrong. | Review recipient formatting and the request payload. |
| Wrong from number | A workflow or API request is trying to send from a number that is not assigned to your account. | Confirm the sending number is one of your assigned Sendblue numbers. |
| Opt-out / suppression | The contact previously told you to stop or unsubscribe. | Check whether the recipient opted out and confirm whether they later replied START. |
| Daily capacity / rate limits | Sends stop after volume spikes or after many new contacts were added in a day. | Review usage and pacing. |
| Line health / delivery issues | Formatting and limits look normal, but failures cluster on one line. | Check line-health indicators and reach out to support with examples. |
Fast Triage Checklist
Confirm the recipient number is valid and includes the area code or full international format when required.
Confirm the sending number is actually assigned to your Sendblue account.
Check whether the recipient opted out previously.
Check whether you hit a daily usage limit or rate limit.
If the issue clusters on one line, review line health and blockages next.
When to Contact Support
You have multiple examples that fail even though formatting and sending number are correct.
One line is clearly underperforming while others are healthy.
You are seeing a cluster of delivery errors and cannot tell whether it is account configuration or line health.