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SMS messages sent from Zuper Connect US numbers are subject to carrier requirements for registration, sending speed, daily volume, message length, content, and customer consent. This article explains the limits that apply to Zuper Connect SMS on US 10DLC numbers and how to maintain reliable message delivery.
Applies to: Zuper Connect SMS on US 10DLC numbers

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Before you can send SMS

SMS cannot be sent from a Zuper Connect number until the number’s 10DLC brand and campaign are approved. US carriers require every application-to-person (A2P) sender to be registered and approved before messaging traffic is accepted. Until approval is complete, sending is not enabled on the number.
Warning: Your brand and campaign must both be approved, and the number must be linked to the approved campaign before you can send SMS.

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Why approval is required

Unregistered A2P traffic can be blocked or silently filtered by carriers. This can cause messages to appear as sent even though the recipient never receives them, with no reliable delivery error available for diagnosis. Sending unregistered traffic can also:
  • Result in carrier surcharges or penalties.
  • Damage the reputation of the sending number.
  • Affect the brand’s ability to complete registration successfully later.
All throughput, daily-volume, and message-segment limits in this article apply after approval. Before approval, the effective SMS sending limit is zero. Approval typically takes a few business days after a complete and compliant submission is filed. A common cause of delay is an incomplete or non-compliant customer opt-in and consent flow on the business website.

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How SMS approval works

Approval happens at two levels: Brand and Campaign. Both are required before sending SMS.

Brand

The brand represents your legal business entity. Registration includes your legal business name, EIN, address, and website.Brand vetting produces a Trust Score from 0–100, which affects messaging capacity.

Campaign

The campaign represents the messaging use case, such as customer care, marketing and so on.Campaign registration includes information such as: messaging use case, sample messages, consent language, and customer opt-in process.
Note: A phone number can belong to only one campaign at a time.
The number can only send the type of content approved for that campaign. For example, sending marketing messages through a customer-care campaign is a compliance violation even if the number itself is approved for messaging.

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SMS throughput limits

Carriers measure sending speed in messages per second (MPS). One MPS limit applies per approved campaign and is shared across all long-code numbers linked to that campaign.

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SMS throughput by Trust Score

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Other throughput cases

Sole Proprietor brands have an approximate ceiling of 1 MPS.Carrier limits include:
  • AT&T: 0.25 MPS
  • T-Mobile: 1 MPS per number
  • Verizon: 1 MPS per number
AT&T also limits Sole Proprietor brands to 15 messages per minute.
Low Volume Mixed and Marketing campaigns have a fixed throughput of:3.75 MPS totalThis applies regardless of Trust Score.
Minor carriers representing less than approximately 5% of the market generally support 1 MPS per number. US Cellular supports up to 8 MPS.
Some campaign types have fixed allocations that do not depend on Trust Score, including charity, political, K-12 education, emergency services, and franchise or agent use cases.See Special-use-case limits for details.

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MMS throughput limits

Following the March 2026 carrier update, MMS throughput is also based on Trust Score. Previously, MMS used a flat 1 MPS limit per account.

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What happens when you exceed the sending rate

Messages sent faster than the approved throughput are queued, not immediately rejected. Queued messages are processed at the allowed sending rate. If a message remains queued for more than 10 hours, it is dropped as a queue-overflow failure.
Error 30001 — Queue overflow
A large bulk send can still be delivered, but delivery may be slow. Avoid placing large bulk sends ahead of time-sensitive traffic such as:
  • Appointment reminders
  • Technician en-route alerts
  • Service notifications
Bulk traffic can delay these messages while the queue is being processed.

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T-Mobile daily messaging limits

T-Mobile is the only major carrier that also applies a daily volume limit. This is one of the carrier limits approved senders are most likely to reach. The limit counts:
  • SMS segments
  • MMS messages
Only traffic sent to T-Mobile recipients counts toward the T-Mobile daily allowance.

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How the T-Mobile daily limit works

1

The limit applies per brand

The limit applies to the brand or EIN.
It does not apply separately to individual campaigns or phone numbers.
Every approved campaign and number under the same legal business entity draws from the same daily pool.
2

The limit is shared across messaging providers

If the same EIN is registered with another messaging provider, messages sent through that platform also count toward the same T-Mobile daily allowance.
3

The limit resets at midnight Pacific Time

The daily allowance resets at 12:00 AM US Pacific Time, not according to the customer’s local timezone.

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Russell 3000 businesses

Businesses listed in the Russell 3000 Index receive a default T-Mobile allowance of 200,000 messages per day. Businesses requiring more than 200,000 messages per day must complete T-Mobile’s Special Business Review.

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T-Mobile usage warnings and failures

T-Mobile generates advisory notifications as usage approaches the daily allowance. When the daily limit is reached, messages to T-Mobile recipients fail with 30023 — Daily message cap reached. Messages continue to fail for the remainder of that Pacific-time day.

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SMS message length and segments

An SMS message can use one or more segments. The number of characters available in each segment depends on the message encoding.

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GSM-7 messages

A standard GSM-7 message supports up to 160 characters in one SMS segment. If the message exceeds 160 characters, it is divided into multiple segments. Because concatenated segments include a header that allows the recipient’s device to reassemble them, each segment can contain up to 153 characters. Example:
  • 160 GSM-7 characters = 1 segment
  • 161 GSM-7 characters = 2 segments
The recipient’s phone typically reassembles the segments and displays them as a single message.

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UCS-2 messages

Messages containing characters outside the GSM-7 character set use UCS-2 encoding. These characters commonly include:
  • Most emoji
  • Many accented characters
  • Many non-Latin characters
A UCS-2 message supports 70 characters in one segment. For concatenated UCS-2 messages, each segment supports 67 characters. Example:
  • 70 UCS-2 characters = 1 segment
  • 71 UCS-2 characters = 2 segments
A single non-GSM character, such as an emoji, can cause the entire SMS to use UCS-2 encoding.

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Maximum SMS length

The platform supports a maximum of 1,600 characters per message. Messages above this limit fail with 21617 — Message exceeds the supported length. Inbound messages above the limit are truncated. Carriers may also reject long UCS-2 messages before they reach the 1,600-character platform limit. These failures can return 30019.
For more reliable delivery, keep SMS messages to approximately 320 characters or fewer. This is roughly equivalent to two SMS segments.

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Why SMS segments matter

T-Mobile’s daily allowance counts segments, not simply the number of messages submitted. This means one long SMS can consume several units of the daily allowance even though the recipient sees a single message. For example, a 400-character message containing one emoji can consume approximately six SMS segments because the emoji changes the message encoding to UCS-2. A single emoji can therefore significantly increase daily segment consumption. Recommended practices:
  • Keep templates short.
  • Stay within one GSM-7 segment when possible.
  • Avoid unnecessary emoji in high-volume templates.
  • Review special characters before sending large campaigns.
  • Reduce unnecessary message text where practical.
Short, GSM-7-compatible templates are one of the simplest ways to preserve messaging capacity.

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Content and consent requirements

Campaign approval authorizes a particular messaging use case. It does not prevent individual messages from being filtered. Filtered messages typically return 30007 — Message filtered, and the carrier may not provide a detailed reason for the filtering. Because of this, prevention is more useful than trying to diagnose individual filtered messages after they occur.

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Prohibited and restricted content

Carrier restrictions apply to prohibited and high-risk messaging categories, including:
  • Sex-related content
  • Hate-related content
  • Alcohol
  • Firearms
  • Tobacco
  • Cannabis and CBD
  • High-risk lending
  • Debt collection outside permitted rules
  • Gambling
  • Third-party lead generation
These categories are commonly associated with the carrier restrictions referred to as SHAFT and related prohibited-use policies. Consent must match the approved campaign use case. For example, consent to receive transactional or customer-care SMS does not automatically authorize promotional SMS. Promotional messaging requires separate and explicit consent where applicable.

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SMS opt-out requirements

Opt-out requests must be honored automatically. The following keywords must stop messaging to the recipient:
  • STOP
  • END
  • QUIT
  • CANCEL
  • UNSUBSCRIBE
The keyword HELP must return the configured support information.
Continuing to send SMS to a recipient who has opted out can violate carrier requirements and may create TCPA exposure.

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Link and content best practices

To reduce the risk of carrier filtering:
  • Use a branded URL domain.
  • Avoid public URL shorteners such as bit.ly and TinyURL.
  • Identify the sender clearly.
  • Avoid excessive capitalization.
  • Avoid excessive punctuation.
  • Send only content that matches the approved campaign use case.
  • Maintain valid customer consent.
Repeated violations can cause an approved campaign to be suspended. When a campaign is suspended, SMS sending is disabled until the compliance issue is resolved.

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Special-use-case limits

Some campaign types receive fixed allocations that do not depend on the standard Trust Score bands.

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Current provider position: Plivo to Twilio

Zuper Connect accounts are currently provisioned on Plivo. Zuper is migrating accounts and phone numbers to Twilio. Plivo is therefore a temporary provider position during this transition. The 10DLC approval requirement applies to both providers.

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Current Plivo limits

Plivo currently publishes the following limits and recommendations.
Plivo supports up to 4,500 transactions per minute per operator, which is approximately 75 MPS. The actual rate depends on brand and campaign characteristics.
For a standard brand:
  • Maximum campaigns per brand: 3
  • Maximum long-code numbers per campaign: 49
  • Each phone number can belong to only one campaign.
Approximate T-Mobile allowance: 1,000 segments per dayApproximate allowance across US carriers: 3,000 segments per day
Approximate T-Mobile allowance: 2,000 segments per dayApproximate allowance across US carriers: 6,000 segments per day
Russell 3000 brands receive: 200,000 messages per day to T-Mobile
Plivo recommends optional brand vetting for businesses sending more than approximately:6,000 messages per day
Note: Plivo does not currently publish a per-carrier, per-Trust-Score breakdown. The underlying carrier limits described earlier in this article come from AT&T, T-Mobile, and Verizon through the industry registry rather than being provider-specific limits.

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After migration to Twilio

After migration, Zuper follows Twilio’s published carrier figures. The SMS, MMS, Trust Score, and daily-volume tables in this article represent the limits Zuper uses for capacity planning and support after the account and phone numbers move to Twilio.

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Important considerations during migration

10DLC registration is provider-specific. A campaign approved on Plivo must be registered and approved again on Twilio. The migrated phone number cannot send SMS through Twilio until that approval is complete.
T-Mobile applies its daily allowance at the brand or EIN level across messaging platforms. If some phone numbers remain on Plivo while other numbers have migrated to Twilio, messages from both providers draw from the same T-Mobile daily allowance.

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How to get SMS sending approved

  1. Submit the brand. Provide information that matches public business records exactly, including legal business name, EIN, registered business address, and website. Mismatched information is a common reason for a low Trust Score, registration delays, or registration rejection.
  2. Publish a compliant customer opt-in flow. Publish the opt-in process before submitting the campaign, since carriers can verify the customer consent flow during review. The customer-facing form must include an explicit SMS consent checkbox. The checkbox must not be selected by default and must be separate from general Terms and Conditions acceptance. The business must also include corresponding SMS language in its Privacy Policy and Terms of Service. Verbal-only consent generally does not pass review unless evidence of the consent process is available on a publicly accessible page.
  3. Declare the correct messaging use case. Select the campaign use case that accurately represents the messages the business intends to send. If the business sends both service or transactional notifications and marketing or promotional messages, these require separate consent and may require separate campaigns.
  4. Wait for complete approval. Do not schedule SMS sending until approval is confirmed. Brand approval by itself is not sufficient. Confirm that the brand is approved, the campaign is approved, and the phone number is linked to the approved campaign.

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How to increase messaging limits

After approval, use the following options to increase available messaging capacity. Complete brand vetting Trust Score is one of the main factors determining both throughput and the T-Mobile daily allowance. An unvetted brand can be limited to 12 MPS and 2,000 T-Mobile segments per day. A highly vetted brand can reach 225 total MPS and 200,000 T-Mobile messages or segments per day. Shorten SMS templates Keep templates within one GSM-7 segment whenever possible. This reduces segment consumption and preserves daily messaging capacity. Keep filtering rates low Maintain valid consent, compliant content, correct campaign use, and clean opt-out handling. Clean sending behavior helps protect the messaging capacity already available to the business. Request T-Mobile Special Business Review If the business needs to send more than 200,000 messages per day to T-Mobile, request T-Mobile Special Business Review through Zuper.

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Troubleshooting

Possible cause: The brand or campaign is still pending, the campaign was rejected, or the phone number has not been linked to the approved campaign.What to do: Confirm that the brand is approved, the campaign is approved, and the number is linked to the approved campaign. Do not treat brand approval alone as authorization to send SMS.
Possible cause: The campaign is sending messages faster than its approved throughput.What to do: Reduce the sending rate or allow queued messages to process. Avoid placing bulk campaigns ahead of time-sensitive operational messages.
Cause: The message remained queued for more than 10 hours.What to do: Reduce bulk traffic or pace sending according to the approved campaign throughput.
Cause: The business reached its T-Mobile daily allowance.What to do: Wait until the allowance resets at midnight US Pacific Time. If this occurs regularly, review the brand Trust Score, shorten templates, reduce unnecessary SMS segments, or request additional review if the business qualifies.
Cause: Approximately 50% of the T-Mobile daily allowance has been consumed.What to do: Review the remaining traffic planned for the day.
Cause: Approximately 70% of the T-Mobile daily allowance has been consumed.What to do: Prioritize important messages and reduce unnecessary multi-segment traffic.
Cause: The SMS contains more than 1,600 characters.What to do: Shorten the message and send it again.
Possible cause: A carrier rejected a long UCS-2 message.What to do: Shorten the message. Where appropriate, remove unnecessary emoji or other non-GSM characters.
Possible cause: The carrier filtered the message because of message content, missing or inappropriate consent, campaign-use-case mismatch, sender reputation, public URL shorteners, or restricted or prohibited content.What to do:
  1. Confirm that the message matches the approved campaign.
  2. Confirm that the recipient provided the appropriate consent.
  3. Confirm that the recipient has not opted out.
  4. Remove prohibited or high-risk content.
  5. Replace public URL shorteners with a branded URL.
  6. Avoid unnecessary capitalization and punctuation.
Possible causes include:
  • Business information does not match public records.
  • The website does not include a compliant SMS opt-in flow.
  • The SMS consent checkbox is selected by default.
  • SMS consent is bundled with acceptance of general terms.
  • The Privacy Policy does not contain the required SMS language.
  • The Terms of Service do not contain the required SMS language.
  • The campaign use case does not match the sample messages.
  • The consent process does not match the declared campaign.
Review and correct the submitted information before resubmitting.

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Frequently asked questions

No. The campaign must also be approved, and the number must be linked to the approved campaign.
No. The campaign’s MPS allocation is shared across all numbers linked to that campaign.
No. T-Mobile applies the daily allowance at the brand or EIN level.
Yes. If the same EIN is registered on multiple messaging platforms, traffic from those platforms counts toward the same T-Mobile allowance.
Not necessarily. Long SMS messages are divided into segments, and T-Mobile counts each segment toward the daily allowance.
Yes. Most emoji cause the message to use UCS-2 encoding, which reduces the number of characters supported per segment and can significantly increase segment consumption.
No. Only send message content that matches the campaign use case approved by the carrier.
SMS sending for the affected campaign is disabled until the compliance issue is resolved and the campaign is restored.
At midnight US Pacific Time.
Public URL shorteners can increase the risk of carrier filtering. Use a branded URL domain whenever possible.

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Best practices

  • Complete both brand and campaign approval before sending SMS.
  • Match registration information to public business records.
  • Publish a compliant SMS opt-in process before campaign submission.
  • Keep SMS templates short.
  • Use GSM-7 characters when practical.
  • Avoid unnecessary emoji in high-volume templates.
  • Keep time-sensitive messages separate from large bulk sends.
  • Monitor T-Mobile daily usage.
  • Use branded URLs.
  • Clearly identify the message sender.
  • Maintain valid customer consent.
  • Honor opt-out requests immediately.
  • Only send content covered by the approved campaign.
  • Complete brand vetting when higher throughput is required.

10DLC Registration

Register a brand and campaign for A2P messaging.

Port a Number

Bring an existing phone number into Zuper Connect.

Conversations

Manage SMS and messaging conversations in Zuper Connect.

Twilio Integration

Set up Twilio as a messaging provider.