Common SMS Delivery Errors in Sparkforge and How to Fix Them

By Sparkforge Support Team ·Last reviewed May 3, 2026

SMS errors in Sparkforge come back as numerical codes from the carrier or messaging provider. Each code points to a specific cause like opt-outs, carrier filtering, or unreachable handsets, with a matching fix.

Where SMS errors come from

Most SMS delivery errors originate from the carrier or messaging provider and surface in Sparkforge as numerical codes. Identifying the code lets you take the right action quickly without guessing at the cause.

Find the error code

Open Conversations.
Search for the failed SMS log.
Click the unsuccessful conversation.
Hover the red triangle error box to see the code and short description (for example, Error 30034 or Error 21610).

Common error codes

Error 11751 — Media message size limit exceeded

The MMS file is larger than the carrier or provider allows. Compress or resize the file. US and Canada MMS caps at 5MB per message.

Error 21610 — User opted out

The recipient replied STOP. Don't message this number again unless they reply START to opt back in. Tighten your opt-in flow to reduce repeat opt-outs.

Error 21612 — Unreachable 'To' number from current sender

The destination can't be reached from the From number, often because of carrier restrictions or unsupported international routing. Use a local number or one enabled for international sending and confirm routing compatibility.

Error 30002 — Account suspended before delivery

The provider account was suspended between send and delivery. Contact your provider's support to restore the account and keep status active.

Error 30003 — Unavailable or inactive number

The recipient phone is off, out of range, or temporarily unavailable. Retry later and verify the number is active.

Error 30004 — Message blocked by carrier

The destination is blocked from receiving the message. Confirm the number is valid and not flagged. Stop messaging numbers with repeated failures.

Error 30005 — Unknown destination handset

The device is unreachable for an extended period. Retry later and clean your list to remove dead numbers.

Error 30006 — Landline or unsupported number

The number can't receive SMS, usually because it's a landline. Run number validation on your list to remove landlines before sending.

Error 30007 — Carrier filtering

The carrier blocked the message for a spam or policy violation. Review content for risky keywords, confirm 10DLC or toll-free registration is in place, and remove links or formatting that trip filters.

Stay ahead of errors

Maintain proper opt-in records, keep your A2P 10DLC or toll-free registration current, and clean inactive numbers regularly. Each step lifts deliverability and keeps your sender reputation intact.

Frequently Asked Questions

How do I find the error code for a failed SMS?

Open Conversations, click the failed message, and hover the red triangle. Sparkforge shows the numerical code and a short description.

What does Error 21610 mean?

The recipient opted out by replying STOP. Don't message the number again unless they reply START to opt back in.

How do I fix Error 30007 carrier filtering?

Review the message for spam keywords or risky links, confirm A2P 10DLC or toll-free registration, and verify your sender complies with carrier policies.

Why does Error 30006 keep happening?

The number is a landline or otherwise can't receive SMS. Run number validation against your list to remove landlines before sending.

How can I prevent SMS delivery errors?

Keep opt-ins clean, complete A2P 10DLC or toll-free registration, scrub your list to remove inactive numbers, and avoid carrier-flagged content patterns.