Overseas Carrier Screening Methodology: How to Identify High-Value Numbers and Assess Empty Number Risks

In the practical application of cross-border business and overseas user growth, overseas operator screening is the fundamental capability that determines number quality and reach effectiveness. Many teams spend significant resources procuring number resources, only to frequently encounter pitfalls due to their inability to distinguish the operator attributes behind the numbers. A systematic methodology for overseas operator screening can help you eliminate invalid and low-value numbers from the source, ensuring that every batch of numbers is truly usable. Having worked in overseas number quality analysis and operator identification for five years, and having processed over 30 million global number data points, I will share a practically proven screening method below.

I. Why is screening overseas operators the starting point for number quality management?

Many companies purchase seemingly large lists of phone numbers when expanding into overseas markets, but the actual usability rate is often less than 50%. Using numbers without operator screening can lead to the following problems:

• Risk of invalid phone number : The number has been cancelled or not assigned, and messages cannot be routed at all.

• Low-activity users : The number belongs to a low-consumption prepaid user and has been inactive for a long time.

• Carrier restrictions : Some smaller carriers have strict firewalls on international messages, resulting in extremely low delivery rates.

• Cost out of control : Invalid numbers consume verification fees, sending fees, and manual follow-up costs.

The value of a phone number is never based on "quantity," but on "identifiable carrier attributes." Overseas carrier screening = identifying numbers from mainstream physical carriers + eliminating invalid and inactive numbers; this is the core starting point for number quality management.

II. Layered Identification Methods of Major Global Operators

Operators in different countries and regions vary greatly in terms of number stability, activity levels, and international compatibility. A hierarchical identification logic needs to be established.

• **Tier 1 Mainstream Carriers**: Such as T-Mobile/AT&T/Verizon in the US, EE/Vodafone in the UK, and Telekom in Germany. These carriers have long number lifecycles and high customer loyalty, making them the highest priority.

• **Tier 2 Regional Operators**: Such as Optus in Australia and Rogers/Bell in Canada. Coverage is limited, but quality is stable within the local area, serving as a supplement.

• **Tier 3 Virtual Network Operator (MVNO):** These lease physical networks, but their number behavior varies significantly, with short active periods. Downgrading or using them solely for testing is recommended.

• **Exclusion Categories:** Known empty number ranges, deactivated number ranges, and operators with a long history of inactivity.

Practical recommendations: In the number cleaning process, prioritize retaining numbers from Tier 1 and Tier 2 operators. Tier 3 numbers should be retained at no more than 20% of the total and monitored separately. Operator numbers that fail to respond after three consecutive calls should be directly blacklisted.

III. Techniques for Identifying and Verifying the Risk of Invalid Numbers

Empty phone numbers are the most common trap in phone number procurement. The prefix of the number segment cannot completely determine whether a number is empty; multiple layers of verification are required.

• MCC+MNC cross-check : Check if the number's mobile country code and mobile network code are in the valid operator's registry. If they cannot be found, the number is likely invalid or has been deregistered.

• Status code feedback analysis : During the test transmission, record the status codes returned by the operator. Specific error codes such as "invalid number" or "subscriber not found" are directly marked as invalid numbers.

• Time window verification : Test the same number at three different time points (e.g., morning, noon, and evening). If all three tests return an invalid status, the number is highly likely to be invalid.

• Cost control for batch verification : Each invalid number verification has a cost; therefore, sampling is recommended. Randomly select 200 numbers from 10,000 numbers for verification, and estimate the overall invalid number rate.

Real-world data: In a cleansing operation involving 200,000 North American phone numbers, the three layers of verification mentioned above ultimately identified approximately 16% of invalid and deactivated numbers. Using these numbers directly would result in a waste of nearly one-fifth of the budget.

IV. Screening Logic for Inactive Numbers and Zombie Accounts

The existence of a phone number does not equate to user activity. A large number of prepaid or one-time registration numbers may receive messages, but users will never respond. The screening logic is as follows:

• Prepaid number identification : Inferred from carrier type. T-Mobile has a higher prepaid rate than AT&T and Verizon, and prepaid numbers within the same carrier have significantly lower long-term activity rates.

• Historical Behavioral Cycle : Records changes in the online status of the same number over a 30-day period. Numbers that are always online but never interact can be marked as having "low response potential."

• Registration duration dimension : Newly activated numbers less than 7 days ago indicate unstable user behavior. Numbers registered more than 6 months ago with no interaction history show a continuously declining activity probability.

• Regional aggregation judgment : If more than 60% of the numbers in the same number segment have not responded within 30 days, the entire number segment can be temporarily downgraded.

It is recommended to categorize numbers into four levels: "Highly Active," "Mediumly Active," "Lowly Active," and "Suspected Zombie Numbers." Highly and moderately active numbers should be used normally, while lowly active numbers should have their sending frequency reduced. Suspected zombie numbers should be compiled and reviewed collectively or removed directly.

V. Dynamic Number Segment Management and Continuous Update Mechanism

Operators release new number segments periodically, and some previously empty number segments are also reactivated. Static filtering rules will gradually become ineffective over several months.

• We synchronize global number segment change data monthly , focusing on newly activated mainstream operator number segments and number segments that have been reclaimed and redistributed.

• Record the actual response rate for each number segment : continuously track the 3-day and 7-day response rates at the number segment level to form a number segment quality score.

• Carrier Announcements and Network Change Tracking : Some carriers proactively announce their number segment adjustment plans in advance, which is more effective than simply being caught off guard.

• Establish a number segment lifecycle table : each number segment is marked with one of four statuses: "Stable and High-Quality", "Under Observation", "Suspended", and "Discontinued", and reviewed every two weeks.

In a Southeast Asian number cleaning project, timely updates to a local operator's number segment change information prevented a large-scale use of abandoned number segments, directly saving approximately 80,000 yuan in costs.

Conclusion

The quality management of overseas phone numbers is essentially a system of identification and stratification centered on operator attributes. From differentiating between mainstream operators and virtual operators, to multi-layered verification of empty number risks, to screening inactive numbers and dynamic management of number segments, each step answers the same question: Is this number worth reaching? Through a standardized overseas operator screening process, the originally chaotic and disordered list of numbers can be broken down into a clear priority queue—high-value physical operator numbers are given priority, inactive numbers are reduced in frequency, and empty and deactivated numbers are directly eliminated. The value of ITG's full-domain screening lies in solidifying this methodology into a scalable and automated tool, freeing practitioners from expending manpower on operator lookups and empty number verification. When each batch of numbers is filtered by operator attributes and scored for activity before being put into use, you will find that truly efficient overseas growth never requires disorderly casting a wide net.