10DLC Error Codes Explained: Troubleshooting Your SMS Campaigns

Your 10DLC campaign got approved two weeks ago. Everything looked fine. Then yesterday morning, 30 percent of your outbound messages started failing. Your dashboard shows error codes you have never seen before, and your messaging provider's documentation gives you a one-line definition that does not actually explain what went wrong or how to fix it.

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You are not alone. 10DLC error codes are some of the most frustrating parts of business messaging. Carrier filtering is aggressive, error messages are vague, and the gap between "your campaign is approved" and "your messages are actually getting delivered" is wider than most businesses expect.

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This guide explains the most common 10DLC error codes, what actually causes them, and specific steps to resolve each one.

How 10DLC Filtering Works

Understanding why errors happen starts with understanding how carrier filtering works. When you send an A2P message from a 10DLC number, the message passes through multiple filtering layers before reaching the recipient.

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First, your messaging provider validates the message against your registered campaign. If the number is not associated with an approved campaign, the message may be rejected at the provider level before it even reaches the carrier.

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Second, the carrier's network filters evaluate the message content, sending patterns, and your Trust Score. Carriers use machine learning models that analyze message content for spam-like patterns, URL reputation, and keyword triggers. Even approved campaigns can have individual messages filtered if the content triggers these models.

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Third, device-level spam filtering on the recipient's phone may block or flag the message after carrier delivery. This is outside your control, but it is influenced by your sender reputation.

The Most Common 10DLC Error Codes and How to Fix Them

Error 30004: Message Blocked by Carrier (The Most Common Problem)

Error 30004 is the error code that causes the most frustration because it tells you the message was blocked but does not tell you why. Carrier content filtering is a black box, and carriers do not publish their exact filtering rules for obvious reasons.

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However, there are known patterns that trigger 30004 errors consistently.

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‍Shortened URLs.

‍Bit.ly, TinyURL, and other URL shorteners are heavily associated with spam and phishing. Carriers aggressively filter messages containing shortened URLs. Use your own branded short domain instead, or include the full URL. If you must shorten links, use a dedicated branded shortener tied to your domain.

URL reputation

‍Even full-length URLs can trigger filtering if your domain has a poor reputation. New domains, domains without proper DNS records (SPF, DKIM, DMARC), and domains that have been flagged by web safety services are all treated with suspicion. Check your domain's reputation before including it in messages.

Spam-like content patterns

‍ALL CAPS, excessive exclamation marks, urgency language like "ACT NOW" or "LIMITED TIME," and certain financial terms can trigger content filters. Write messages the way you would write a professional text to a colleague: clear, direct, and free of hype.

Repetitive content

‍Sending the exact same message text to thousands of recipients is a spam pattern. Personalize your messages with the recipient's name, specific order details, or other variable content that makes each message unique.

High sending rate

‍Sending a large burst of messages in a short window can trigger rate-based filtering. Spread your sends over a longer period rather than blasting your entire list at once.

Error 30007: Carrier Violation

Error 30007 means the carrier specifically identified your message content as violating their policies. This is a step beyond content filtering. The carrier has determined that your message contains prohibited content.

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Common triggers include references to cannabis or CBD (even in states where it is legal), gambling or betting promotions, certain pharmaceutical terms, and content that impersonates government agencies or emergency services.

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If you are receiving 30007 errors and your content does not obviously fall into a prohibited category, the issue may be with your campaign registration. Your registered use case may not match the content you are actually sending. If you registered a "customer care" campaign but are sending marketing promotions, the mismatch can trigger carrier violations.

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Review your TCR campaign registration and ensure your sample messages accurately represent the content you send. If your messaging has evolved since registration, update your campaign or register a new one.

Error 30034: T-Mobile Specific Filtering

T-Mobile uses its own filtering system in addition to the standard 10DLC trust scoring. Error 30034 specifically indicates that T-Mobile's filters have blocked your message.

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T-Mobile is generally the most aggressive carrier when it comes to content filtering. Messages that pass AT&T and Verizon filters sometimes get caught by T-Mobile's system. Common triggers include sending too many messages too quickly, repetitive message content across multiple recipients, and URLs that T-Mobile's systems flag as suspicious.

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If you are seeing 30034 errors, reduce your sending frequency to T-Mobile numbers, vary your message content between sends, and ensure your URLs have clean reputations. If the errors persist, your messaging provider can engage with T-Mobile on your behalf to investigate the filtering.

Preventing 10DLC Errors Before They Happen

Validate your contact list

‍Run every number through a phone number lookup before adding it to your messaging database. Remove landlines, VoIP numbers that cannot receive SMS, and numbers that are no longer in service. A clean list reduces errors by 20 to 40 percent.

Match your content to your campaign registration

‍If your TCR campaign says you send appointment reminders, send appointment reminders. Do not repurpose a transactional campaign for marketing messages. Carriers check for this.

Personalize every message

‍Include the recipient's name, order number, appointment time, or other specific details. Personalized messages are less likely to trigger spam filters and more likely to engage recipients.

Monitor your delivery rates daily

‍A sudden drop in delivery rate is an early warning sign. Investigate immediately rather than waiting for the problem to escalate. Your messaging provider should offer delivery analytics that let you spot trends before they become outages.

Use a provider that monitors proactively

‍Signalmash monitors customer messaging traffic and alerts you to delivery anomalies before you notice them yourself. Their engineering team can investigate carrier filtering issues directly through their Tier-1 carrier relationships, which is significantly faster than navigating carrier dispute processes on your own.

When to Escalate to Your Provider

Some 10DLC errors are self-fixable. Clean your list, adjust your content, and the errors stop. Others require provider-level intervention.

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Escalate when you see consistent 30004 or 30007 errors across clean, compliant messages. When your delivery rate drops below 90 percent without an obvious content or list quality issue. When T-Mobile filtering blocks messages that AT&T and Verizon deliver successfully. When you receive a campaign suspension notice from TCR or a carrier.

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Signalmash's dedicated Slack support means you can escalate in real time rather than waiting for a ticket response. Their engineering team has direct relationships with carrier filtering teams and can investigate and resolve issues faster than providers that route everything through standard support channels.

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10DLC errors are a reality of business messaging in 2026. The difference between a frustrating experience and a manageable one is how quickly you identify the cause and how effectively your provider helps you resolve it.