SMS and RCS permissions: How to build a high-performing permission base

If you want to succeed with SMS and RCS marketing, permissions are not just a legal requirement – they are the foundation of performance. A properly built permission base delivers higher engagement, stronger relationships and better results on mobile.

This article is for people working in marketing or e-commerce who use — or are considering using — SMS and RCS for marketing messages.

SMS and RCS are among the most direct and personalised channels in your marketing mix. When a customer gives you permission to send marketing messages to their mobile, you gain access to a channel where relevance, timing and clear value can translate directly into engagement, sales and loyalty.

In this article, we guide you through how to build a permission base for SMS and RCS that truly delivers value. You'll get an overview of what permission marketing is — and isn't — how consent works across SMS and RCS, and which methods work best when collecting permissions in practice.

What is permission marketing?

Permission marketing is essentially about communicating only with recipients who have actively agreed to hear from you. Rather than interrupting people with unwanted messages, you build relationships based on clear consent and a clear expectation of what the recipient will gain from being on your mobile list.

You have probably already encountered permission marketing — for example when you sign up for a newsletter or agree to be contacted by phone by a company. The common denominator is that communication only starts when you have given your authorisation.

In practice, this means that SMS and RCS are not channels you can just start using — they have to be earned. When a customer gives you permission to send marketing messages to mobile phones, they have made a conscious choice because they expect something valuable in return, for example relevant offers, early access, inspiration, invitations or exclusive benefits.

For marketing and e-commerce, permission marketing is particularly effective because it creates a more engaged audience. Recipients are already interested in your brand, which provides ideal conditions for clicks, conversions and long-term loyalty. That is why the quality of your permissions is generally more important than the quantity.

Permission marketing is not just about what you can send. It's a strategic choice to communicate in a way that emphasises relevance, timing and value — especially when working with channels as personal as SMS and RCS.

What is a permission - and what is it not?

A permission is a specific authorisation from the recipient for you to send marketing messages on a specific channel — for example, SMS, RCS or email. It is given voluntarily, with the expectation that the communication will be perceived as relevant and valuable. In practice, the terms permission, authorisation and consent are often used interchangeably.

Permission is not a blank cheque to send anything, anywhere. Consent implies a clear expectation that you will only use the channels the recipient has actively agreed to, and that your messages are relevant to the recipient.

Permission is, in practice, as much about aligning expectations as it is about consent. The clearer you are about what the recipient has agreed to, and the better you live up to it, the stronger the relationship will be. This applies whether you communicate via SMS, RCS or e-mail.

It's also important to distinguish between the legal and the commercial. Legally, permission is about whether you may send marketing on a given channel. Commercially, it is about whether the recipient wants to keep hearing from you. Here, relevance, timing and clear value are what determine whether your permission base grows over time.

A permission is therefore not a guarantee of engagement — but an opportunity. The better your messages match the recipient's expectations and interests, the stronger the results you can achieve with your permission marketing efforts.

SMS and RCS: Same consent, different expectations

When it comes to mobile consent, SMS and RCS are treated the same. If a recipient has given permission to receive marketing messages on their mobile phone, the consent applies to the channel they agreed to, whether the message arrives as a standard SMS message or as RCS.

In practice, both RCS and SMS are typically sent via an SMS gateway, where you can manage campaigns, opt‑outs and integrations in the same system.

However, this does not mean the expectations for the two formats are the same. SMS is a familiar, straightforward format that most people associate with short, direct messages. RCS is more visual and interactive, resembling an app‑like experience. It affects how the recipient perceives your content and what they expect to gain from being signed up.

RCS offers more ways to showcase products, highlight messages and drive engagement directly within the message. At the same time, it places higher demands on relevance and timing. The more content and visual space available, the more important it is that the message feels valuable to the recipient.

Therefore, it is a good idea to think of SMS and RCS as two different expressions of the same relationship. The consent is the same, but the experience differs. While SMS is well suited to short, time‑critical messages, RCS offers more scope for inspiration and deeper engagement without compromising on relevance.

In short: the same consent, different expectations. By tailoring your content to each format, you will get more out of both SMS and RCS.

What the law says - in a nutshell

When we talk about consent in marketing, it is ultimately marketing law that sets the framework. In broad terms, you must have valid consent before you may directly contact a recipient with marketing messages.

Consent must be voluntary, active and informed. The recipient must know who is sending the messages, which channel will be used, and that the content is marketing. In addition, it must always be easy to withdraw consent — for example via an opt‑out link in the message.

It is important to distinguish between marketing and service messages. Service and operational messages, such as order confirmations, delivery updates and other necessary information — often also sent as transactional emails — do not require consent in the same way. It is only when a message has a marketing purpose that the consent requirement comes into effect.

However, we must emphasise that inMobile does not provide legal advice. This article is for guidance only, and it is always your responsibility to ensure you comply with applicable law. Rules may change over time, and in case of doubt we recommend that you seek legal advice or keep up to date via official sources such as the Danish Data Protection Agency's website, the Consumer Ombudsman's website or the Danish Marketing Practices Act.

With the legal foundation in place, you can focus on the most important thing: using your permissions correctly and creating value for those who have opted in to hear from you.

How to build your permission base

A strong permission base does not happen by accident. It is built where your customers are already engaged, and where it makes sense for them to opt in.

What the most effective methods have in common is that they link permission to a clear value and a natural moment in the customer journey. The closer you are to a purchase, an active choice or an ongoing customer relationship, the higher quality your permissions will be — and the better your SMS and RCS communication will perform.

There are many creative ways to collect permissions. Below we outline some of the most commonly used and effective ways to build your permission base.

1. Customer clubs and loyalty programmes

Customer clubs and loyalty programmes are among the strongest sources of permissions. Customers don't just consent to being contacted; they actively choose to enter into a relationship with your brand.

When a customer joins a customer club, the expectation is already set: they want to receive relevant communication, special benefits and content that feels more exclusive than what everyone else gets. This makes the customer club an ideal place to collect permissions and create a foundation for increased customer loyalty.

At the same time, loyalty programmes give you a clear starting point for communicating value. This might include early access to sales, personalised offers, points balance, invitations or product news. The clearer the link between a permission and a benefit, the higher the quality of the permissions you collect.

An important point is that permissions in customer clubs often have a long lifespan. Members have already shown interest and engagement, which means mobile communication here can be used more strategically and relationally rather than just campaign-based. The result is typically higher engagement and fewer unsubscribes.

2. Competitions and polls

Contests and polls are an effective way to collect permissions because they combine low friction with high involvement. The user gets something immediately, while you can quickly expand your permission base.

Competitions work particularly well for engaging new audiences or raising awareness of campaigns, launches and events. Polls are better suited to existing customers and can also provide insights into preferences and interests that can be used for subsequent segmentation.

Competitions and polls are particularly relevant when you want to encourage activity and quickly grow your permission base, especially as an integral part of a campaign where engagement is already the focus.

3. Pop-ups

Pop-ups are one of the most common methods for collecting permissions at scale — and with good reason. They are easy to implement and can be placed exactly where the user is already active on your website.

Pop-ups work best when they appear in a relevant context, for example after a set period, on scroll, on exit intent or on specific pages or products. Better timing increases the likelihood that the user will opt in.

It is crucial that the pop-up is clear and easy to understand. Users should be able to see at a glance what they will receive by signing up and what they are consenting to. Short, clear copy and a single, simple choice make it easier to decide without disrupting the experience.

4. Lead ads

Lead ads are an effective way to collect permissions, as they allow users to sign up directly within the ad without leaving the platform they're already using. Forms are often pre-filled with users' details, which reduces friction and increases sign-up rates.

The method, also known as lead generation, works particularly well on social media, where users are already in a browsing and inspiration mindset. Lead ads are often used to offer something concrete — for example, competitions, early access, exclusive offers, content or participation in a campaign — in exchange for permission.

This also means you can expect a share of quick opt-outs. Some users sign up solely to obtain the specific offer and then unsubscribe afterwards. That's a natural part of how lead ads work and should be expected and planned for.

Use your SMS or RCS communications to demonstrate why staying subscribed is worthwhile — even after the initial incentive has been claimed.

Lead ads are particularly suitable when you want to scale your permission base quickly and reach new audiences who may not be familiar with your business — where volume and reach are prioritised over building long-term relationships from the first contact.

5. Website checkout

The checkout is an obvious place to collect permissions: the user is already an active customer and has taken a tangible step in their relationship with your brand. Trust is typically higher than earlier in the customer journey, and the context makes it natural to offer sign-up for SMS and RCS.

Permissions at checkout are often used to keep customers updated with offers, news or exclusive benefits after purchase. It can also be a way to invite customers to join a customer club or a loyalty programme where mobile communication is part of the experience.

It's important that opting in at checkout is an active choice and not something that feels hidden or imposed. A simple checkbox and a short explanation are often enough to make clear what the customer is consenting to — without disrupting the checkout flow or leaving the customer uncertain about what they have consented to.

Checkout typically yields high-quality permissions because they come from customers who have already shown purchase intent. This makes checkout particularly suitable if you want to build a permission base focused on existing customers and loyalty.

6. From email to mobile permission

Many organisations have already built a solid permission base on email. This makes email an obvious starting point for inviting customers to SMS or RCS as a supplement rather than a replacement.

At the same time, it's normal to encounter some reluctance to share a phone number, as a mobile number feels more personal than an email address for many. That's why the transition works best when it builds on an existing relationship where the recipient already knows your brand.

In practice, the transition can be made via emails where you invite recipients to sign up to receive SMS or RCS messages, offering faster notifications, exclusive access or content better suited to mobile.

When the purpose and the value are clear, many organisations find that the initial reluctance quickly disappears. The result is high-quality permissions because they build on existing engagement, trust and a deliberate choice by the recipient.

Use case: From email to mobile permission

At the home and lifestyle store KAiKU, email has long been a central part of customer communication. Therefore, it was natural to build on the existing email permission when they wanted to extend their communication to SMS.

To get off to a good start, KAiKU sent a well-written email to their mailing list, inviting recipients to receive SMS messages from them as well. The message was simple and focused on what recipients could expect to receive on their mobile phones, including messages about special promotions, events and customer evenings at the store.

The email achieved an open rate of 52.2%, and 6.7% of those who opened it chose to sign up to the SMS list. Overall, 3.5% of all recipients converted to mobile permissions, resulting in 240 new SMS permissions via the email alone.

This case study shows how email can serve as an effective lever for building mobile permissions. By introducing SMS and RCS as a natural next step in the relationship, KAiKU successfully extended their communication to mobile.

Tips for building your permission base

When building a permission base for SMS and RCS, there is rarely a single method that stands alone. The best results come when several approaches are combined and when permission collection is treated as an ongoing part of the customer journey — not as a one-off activity.

Here are some of the tips we repeatedly see among companies that succeed at building their permission base.

#1 Make the value clear

Although methods may vary, there is one constant: users need to quickly understand why it makes sense to opt in to mobile communications. It needn't be complex, but it should be concrete. The clearer the link between opting in and what users will receive, the easier the decision becomes.

#2 Collect in the right context

Timing matters. Permissions work best when collected in situations where users are already engaged — for example, after a purchase, during a campaign, or as part of an existing relationship. That makes opting in feel

#3 Segment at sign-up

If possible, it can be beneficial to segment recipients during the sign-up process. For example, allow users to select areas of interest or the types of messages they want to receive. That gives you greater scope for targeted communication later. However, take care not to make the sign-up process unnecessarily complex.

Summary

Permissions form the foundation of all effective SMS and RCS marketing. Not merely a formality, but a prerequisite for complying with marketing law and for building engagement, relationships and long-term results on mobile.

If you want to succeed with SMS and RCS, the task is clear: build your permission base where customers are already engaged and where it makes sense for them to opt in. This could be at checkout, via customer clubs, through lead ads, competitions, or by inviting existing email subscribers to opt in to mobile communications.

SMS and RCS rely on the same consent, but are used differently. SMS is ideal for short, direct messages, while RCS enables richer, more visual and engaging content. Choosing the format according to the situation and purpose lets you get more out of both channels.

The KAiKU case shows you don't have to start from scratch. Existing relationships, especially via email, are often the best foundation for building mobile permissions, since trust is already established.

In short, start with the relationships you already have. Make it clear why it makes sense for people to hear from you on their mobile. Use SMS and RCS where they make a real difference. That way you will not only build a permission base, but also establish a strong foundation for mobile marketing that can grow over time.