Quick answer
SendGrid documents total message size as Less than 30 MB. The complete request message, including encoded attachments, must remain below the ceiling.
Verified Aug 22, 2026Official source
Current limits
| Constraint | Current value | Scope | Verified source |
|---|---|---|---|
| total message sizeThe complete request message, including encoded attachments, must remain below the ceiling. | Less than 30 MB | Mail Send API | Twilio SendGridAug 22, 2026 |
Why does this limit matter?
Base64 encoding can make an apparently safe source attachment exceed the API message limit.
This value is scoped to Mail Send API; a different plan, runtime, model, endpoint, region, or account can produce a different effective constraint.
What should you check?
- Calculate encoded attachments plus JSON and MIME overhead before sending.
- Confirm the exact plan, model, runtime, endpoint, region, and account that serve the failing workload.
- Record the observed value, response headers or configuration, timestamp, and source without logging secrets.
Important caveats
- Provider and recipient mailbox limits can be lower after SendGrid accepts the request.
- Treat the official source and live account configuration as authoritative if they differ from this verified snapshot.
HyperObserve reports the documented platform constraint. Your application, SDK, gateway, provider, region, or account can impose a lower effective limit.
Related