How to Filter Phone Numbers by Line Type for Better SMS Delivery

You’ve built a contact list, written solid SMS copy, sent SMS to your contact list, and dealt with an underperforming SMS campaign. Do you know the real reason behind it? In most cases, it is not timing or your SMS copy, but it’s your contact list. Your contact list includes landlines and VoIP numbers that can’t receive text messages. As a result, you’re wasting SMS credits , damaging your sender reputation, and getting nothing in return. This is where phone number filtering by line type matters for SMS delivery improvement. It is one of the most overlooked factors for SMS delivery rate optimization.

Let’s understand how it works.

TL;DR

• Sending SMS to landlines and VoIP lowers your delivery rate and burns your budget.
• Phone number filtering by line type lets you target only mobile numbers that receive SMS.
• So, you experience higher SMS delivery improvement, lower costs, and cleaner SMS campaign data.
• Landline Remover is a tool that helps in phone number validation for better SMS delivery.

What is Line Type Filtering?

Every phone number in your contact list belongs to one of three categories. Mobile, Landline, and VoIP.

Line type filtering is the process of checking each phone number in your list and identifying which category it falls into before you send a single message. When you send messages without filtering, you’re only guessing. With filtering, you’re targeting.

How Different Line Types Affect SMS Delivery

Let’s understand how different line types affect SMS delivery.

1. Landlines

Landline numbers can’t receive text messages. So, when your SMS marketing platform tries to send an SMS to a landline, it fails and never reaches the intended person. The damage goes beyond the failed delivery: your sender reputation gets affected, bounce rate increases, and carrier trust scores also drop.

2. VoIP Numbers

VoIP numbers are trickier. Some VoIP numbers, like Google Voice, can receive SMS, but others can’t. Sending an SMS to a VoIP number is a coin flip, and if it fails, it causes the same damage and risks as landlines.

3. Mobile Numbers

Mobile numbers are your target audience. On mobile phones, SMS are delivered, and recipients actually respond. The higher the proportion of mobile numbers in your contact list, the better your SMS deliverability will be.

What Happens When You Don’t Filter

Imagine you have 50,000 contacts in your list and you don’t filter them by line type. Suppose 25% to 30% of those numbers include landlines or invalid VoIP numbers. That means 10,000 to 12,500 messages go nowhere, yet you pay for each SMS you send. As a result, your delivery rate is 75% to 80%. Carriers also notice the bounce pattern, and they may throttle your sending.

Now, imagine you’ve filtered your contact list and sent SMS to only 40,000 numbers, all of which are mobile numbers that can actually receive SMS. This way, you spend less, deliver more, and perform SMS delivery rate optimization.

How Phone Number Filtering Works

Here is the step-by-step process that the Landline Remover tool follows for phone number filtering, and that makes your communication more efficient.

First, log in to Landline Remover.

Once you log in, you will see the home page.

1. You need to upload your contact list.

Whether you want to validate 500 numbers or 50,000, simply import your list. Go to Bulk Upload to upload your contact list, or if you want to check a single number, click on Check Number.

You can upload a list in CSV format.

Want to check a single number? Enter any number that you want to validate.

When you enter a number and click Check, it will give you complete information, including line type, DNC type, and more.

2. Customize your filtering option

If you want to filter out landlines, VoIP, or known litigators, you can customize filtering options to your requirements. The tool removes numbers based on the filtering option you’ve set.

3. Get real-time results

The tool pings carrier data to classify each number as mobile, landline, or VoIP. It also checks the carrier name, which helps with the routing decisions. You can integrate this tool with your SMS marketing platform via API to perform real-time validation and receive instant results.

4. Your clean contact list is ready to download

Once you’ve uploaded your contact list and set filtering options, you can run the file cleaner and download the cleaned list instantly.

Beyond Line Type Filtering: What Should You Filter

Line type filtering is only the starting point. The actual line type filtering goes beyond that and covers DNC registry checks, known litigator identification, and carrier name verification.

When you send SMS to a number registered on a state/federal DNC list , you face legal risk. Therefore, each number in your list should be cross-referenced with the DNC list. A good filtering tool, like Landline Remover, also filters known litigators, helping you avoid costly legal trouble.

Line type filtering also includes carrier name verification. Knowing the carrier can help optimize routing and identify numbers that may be problematic, even if the number is technically classified as mobile.

Common Mistakes Most Teams Make With Contact List Hygiene

Most teams make the following mistakes while maintaining contact list hygiene.

• They filter once and forget it, but numbers change. A mobile number today could be ported to a VoIP number next year. Therefore, regular validation is crucial. At a minimum, teams should perform validation every 2-3 months to keep data accurate.
• Teams think purchased contact lists are clean, but in reality, they’re not. Data vendors rarely use any phone number validation tools and classify numbers by line type. Therefore, you should always use a validation tool to confirm the hygiene of any contact list.
• Sometimes teams ignore VoIP numbers. They only filter landlines and leave VoIP numbers untouched. They should segment them carefully because some VoIP numbers are deliverable and some are not.
• If the list is small, teams skip filtering altogether. But even a list of 1,000 contacts can contain 150 to 200 landlines. That’s nearly 15% to 20% waste.

How to Get Started With Phone Number Filtering

If you’re running an SMS campaign and have not started filtering phone numbers yet, here is how you should start.

• First, upload your contact list.
• Run the list through a phone number validation tool like Landline Remover.
• The tool will remove landlines and flag VoIP numbers according to the filters you’ve set.
• Cross-check the numbers against the DNC and known litigator databases.
• Use the cleaned list for your SMS campaign.
• Integrate API validation to keep the new contact list entries clean from the start.

The entire process can take just a few minutes, but you will experience the impact in your next campaign report.

Clean Your Contact List and Improve SMS Delivery Using Landline Remover

Every SMS sent to a landline number damages the sender reputation you’ve built with carriers over time and wastes your hard-earned money. Phone number filtering is necessary and a fundamental step for any team serious about SMS delivery rate optimization. This step comes before copy, timing, and everything else.

Landline Remover is the tool that helps with it. It validates numbers in real-time and filters them by line type. The tool also checks numbers against state and federal DNC lists and flags known litigators in real time. Whether you want to validate 100 or 10,000 numbers, it processes bulk uploads quickly and integrates via API for teams that need automated validation at scale.

Start with 10 free credits at Landline Remover , clean your list, and experience SMS delivery improvement in no time.