How to build and grow a contact list for SMS marketing

With 98% of 16–24-year-olds and over 80% of people aged 55+ owning a smartphone (Uswitch), SMS remains a powerful tool for businesses to connect with customers. Its near-universal reach and an impressive 98% open rate make it ideal for sending marketing messages, appointment reminders, and time-sensitive alerts.

However, for your SMS campaigns to be successful, you need an engaged list of opted-in contacts. This guide explores how to collect mobile numbers and improve opt-in rates, helping you build a high-performing and compliant SMS contact list.

Why should you build a contact list for SMS marketing?

Building a contact list for SMS marketing allows you to target the right people, improve engagement, and reduce the chances of sending messages to those who aren’t interested. Not only is that a waste of your marketing spend, but sending messages to recipients who have not consented could land you in trouble with the law too.

Having a centralised, accessible database means you can manage and segment your audience efficiently, whether by demographics like age, gender, and location, or behaviour like purchase history and engagement level.

A good contacts list also provides key demographic data, such as age, gender and location, so you can target your campaigns accordingly.

Responsiveness is everything in SMS marketing. When someone opts into SMS communications, you need to make sure they start receiving messages immediately, when their engagement levels are high and before they lose interest. It’s also critical that you can quickly remove anyone who opts out of marketing messages, to avoid breaching data privacy rules and tarnishing your brand’s reputation through unwanted communications.

What are the laws on collecting phone numbers for SMS marketing?

Mobile phone numbers are classed as personal data and, as such, you’ll need to follow the data protection rules in the territories you operate in. Different countries have their own data protection laws but, in general, anyone who holds or processes personal data is expected to safeguard it, and adhere to customer communication preferences. 

GDPR (General Data Protection Regulation) is an EU initiative, and applies to all EU member states, as well as to the wider European Economic Area, which includes countries like Norway and Iceland. 

GDPR was enshrined in UK law before Brexit so the regulations also apply here too. Switzerland, which is in neither the EU nor the EEA, modernised its data protection laws with the introduction of the revFADP in September 2023. 

Learn more: SMS compliance (UK): A guide to SMS marketing regulations

Other data protection laws include the Privacy Act in the US, the Data Privacy Act in Australia and the Privacy Act in New Zealand. 

How to collect mobile numbers for SMS marketing

In recent years, consumers have become more open to sharing their mobile number in exchange for better brand experiences. SMS is now a familiar and trusted channel, used by retailers, delivery firms, healthcare providers and many others. The key is to provide a clear, convenient and compliant way for people to sign up.

Here are some of the most effective ways to collect mobile numbers for SMS marketing:

On your website

Add SMS opt-in options to high-traffic areas such as your homepage, checkout page, and account registration forms. Make sure the language is clear and that customers understand they are agreeing to receive marketing messages by text.

Consent must be given through an unticked checkbox that is separate from your terms and conditions. Keep the process as straightforward as possible to avoid drop-off.

In-store or during phone interactions

If you have a physical store or speak to customers by phone, train staff to ask whether customers would like to receive SMS updates. Use in-store signage or digital forms to support this process, and ensure consent is properly recorded.

If you are collecting numbers verbally, consider using a follow-up confirmation message that allows customers to confirm or opt out.

Via customer service and booking systems

When customers get in touch to make an enquiry or book an appointment, this is a useful moment to ask if they’d like to stay informed by text. Many people appreciate receiving reminders and updates by SMS, particularly when it adds convenience.

Always make it clear what kind of messages they will receive, and offer the opportunity to opt in or choose their preferred channel.

Across other digital touchpoints

Include SMS opt-in fields on newsletter sign-up forms, account settings pages, and feedback surveys. You can also use QR codes or short links in printed materials to direct customers to a mobile-friendly opt-in page.

Practical ways to increase opt-in rates

Once your collection methods are in place, the next step is to improve the number of people who actively opt in. Encouraging consent is not just about where you ask, but how you ask and what you offer in return.

Here are proven strategies to help increase opt-in rates:

Competitions and giveaways

Promotions are an effective way to quickly grow your contact list. Offer a compelling prize, and clearly explain that entering includes signing up to receive SMS communications. This approach works particularly well when promoted through social media or email.

Follow up with a welcome message and a reason to stay subscribed, such as an exclusive offer.

Subscriber-only offers

Offering something of immediate value can significantly increase opt-in rates. This could be a discount code, free delivery, or early access to a sale. Make it clear that these benefits are only available to SMS subscribers.

Urgency and relevance can also help. For example, you could try adding a time-limited offer available to new sign-ups via your website.

Create a VIP or loyalty experience

Positioning your SMS list as an exclusive club can increase its appeal. Subscribers could receive behind-the-scenes content, first look at new products, or access to members-only events. This not only drives sign-ups, but also encourages long-term engagement.

Promote your SMS list across all channels

Use your existing marketing channels to encourage sign-ups. Include calls to action in your emails, social media posts, printed materials and customer communications. Be consistent in the message and clear about the value of joining.

Keep the message clear and benefit-led

Be transparent about what customers will receive and how often. Avoid overpromising, and focus on how SMS updates will be useful, timely or rewarding. The more relevant the message, the more likely people are to sign up and stay subscribed.

Managing and maintaining your contact list

A good SMS contacts list is dynamic.

You need to be proactive in building it and managing customer preferences, including opt-outs. This ensures that the people you’re targeting are engaged and more likely to respond to your messages.

Follow these steps for effective contact list maintenance:

Keep your data accurate and current

Over time, mobile numbers can become outdated or invalid. Regularly reviewing your contact list helps reduce message failures and ensures your campaigns reach the right people. Remove duplicate entries and correct formatting issues to keep your data clean.

If customers change their contact preferences or unsubscribe, update your records promptly to reflect this.

Respect opt-outs

Customers must be able to opt out easily at any time. Every marketing message you send should include a clear opt-out mechanism, such as a reply keyword or a link to manage preferences. These requests should be actioned immediately to avoid compliance issues and maintain trust.

Use segmentation for better results

Dividing your contact list into smaller groups based on location, purchase history or engagement level allows you to send more relevant messages. Targeted campaigns often perform better because they speak directly to the needs and interests of each audience segment.

Monitor performance and engagement

Track open rates, click-through rates and opt-out levels to understand how your audience is responding to your SMS marketing. This insight helps you refine your messaging and adjust your strategy to improve future results.

Simplify with the right tools

Using a reliable SMS platform like Esendex allows you to manage your contact list with confidence. You can add contacts manually or in bulk, create groups, schedule campaigns, and automate opt-out processing all from one secure system.

We’ve designed the Esendex platform to make this process as simple as possible, allowing you to add contacts manually, or in bulk; edit details; create groups; and manage opt-outs. 

Find out how Esendex can support your campaigns with our suite of business SMS solutions.