Custom SMS: How to Send Personalized Text Messages in Bulk?

Custom SMS is a business text message personalized with recipient data such as a name, order number, location, purchase history, or behavior. A single template can produce a relevant message for every contact, making it possible to send personalized text messages in bulk without writing each one manually.

Here, custom SMS means personalizing message content. It does not mean changing a phone's messaging app or notification sound, and it is different from a custom SMS Sender ID, which changes the name or number shown as the sender.

Below, you'll learn how personalized SMS marketing works, which data and variables to use, and how to prepare, test, and send a campaign at scale.

What Is Custom SMS?

Custom SMS combines a reusable message template with recipient-specific data. The platform replaces variables in the template with the correct values at send time, so each person receives content connected to their profile, preferences, or activity.

Also called personalized text messages, this approach is used across a wide range of business contexts:

• Promotional campaigns (discounts, offers)
• Order updates and shipping notifications
• Appointment reminders
• Customer re-engagement
• Product recommendations

On the business side, custom SMS lets you reuse templates, automate sending times, and target segments based on relevant customer data. It can support marketing, customer service, and transactional updates without requiring a separate message to be written for every recipient. On the business side, custom SMS lets you reuse templates, automate sending times, and target segments based on relevant customer data. As one of the most effective SMS marketing techniques, it can support customer service, and transactional updates without requiring a separate message for every recipient.

Custom SMS Content vs. a Custom SMS Sender

Message personalization changes what the text says. A custom SMS sender, or SMS Sender ID, changes the name or number displayed as the source. An alphanumeric Sender ID can show a brand name and is generally used for one-way messaging, while a numeric sender may support replies. Availability, registration, and formatting rules vary by destination country and carrier, so confirm the requirements for every market before sending.

You can use personalized content without an alphanumeric Sender ID, and you can use a branded Sender ID without personalizing the message body. Many business campaigns use both, but they solve different problems.

Learn how SMS Sender IDs work and how to get one →

Why Use Personalized SMS?

• Higher engagement:
  Custom SMS stands out because it feels relevant at first glance. When recipients see their name, recent activity, or a context-aware message, they are more likely to open and read it immediately.
• Clearer next steps:
  A message tied to a specific cart, order, appointment, or offer can direct the recipient to one relevant action without the ambiguity of a general broadcast.
• Better conversion:
  Messages that align with user intent — such as abandoned cart reminders or targeted discounts — reduce friction in decision-making. Instead of pushing generic promotions, personalized messaging delivers the right content at the right moment, increasing the likelihood of clicks, purchases, or other desired actions.
• Improved customer experience:
  Personalization signals that a business understands its customers. Rather than receiving irrelevant messages, users get communication that matches their needs or interests. This reduces opt-outs and strengthens long-term engagement.

How to Send Custom SMS with Personalized Fields?

Sending personalized SMS at scale doesn't mean writing thousands of individual messages. It's about using structured data, templates, and automation.

Step 1: Collect Customer Data (With Consent)

Start by building a contact list with proper user consent. This is not only a best practice but also a legal requirement in many regions.

At a minimum, collect:

• Phone numbers
• Names

For better personalization, include:

• Purchase history
• Location
• Preferences
• Interaction behavior

You can gather this data through website forms, landing pages, app sign-ups, surveys, or events. Always make it clear what users are signing up for and allow easy opt-out options.

Step 2: Choose an SMS Marketing Platf orm

Once you have the data, you need a dedicated bulk SMS service provider to send messages at scale. Unlike sending from a personal number, a business SMS platform provides the infrastructure for bulk delivery, contact management, dynamic personalization, compliance, and reporting — all in one place.

Tools like EngageLab allow you to import and manage contact lists, create templates, insert personalization fields, and track delivery performance. The key is choosing a platform that balances usability, scalability, compliance and marketing cost.

Before choosing a platform, check whether it supports:

• Dynamic variables or merge fields and fallback values for missing data
• Audience segmentation, consent records, suppression lists, and opt-out handling
• Message previews using real sample data
• Encoding and SMS segment-count checks after variables are inserted
• Sender options and registration guidance for each destination country
• Delivery reporting, link tracking where applicable, API access, and automation

SMS Customization by EngageLab

Sign up for EngageLab and follow the steps below.

Step 3: Import Data and Organize Your Contact List

Not all customers should receive the same message. Before importing, think about how to segment your list — new vs. returning customers, location, product category interest, or engagement level. Segmentation is what turns basic personalization into genuinely relevant communication.

Once you log into EngageLab, click SMS.

You'll see the Send Message section. Click Input File in the Recipient Number area, then add contact numbers manually or by importing a file. Create separate lists for each segment so each group receives the most relevant message.

Step 4: Create SMS Templates with Variables

Instead of writing separate messages for each recipient, create a single template with dynamic placeholders — and the platform fills in each person's real data automatically at send time.

Common variables include [Name], [Product], [Order Number], [Date], and [Discount Code]. The more relevant data you have in your contact list, the more specific and effective your templates become.

In EngageLab, navigate to Templates and click Create Template. Write your message and insert the personalization variables where needed.

Once you're done, click Submit Audit.

Step 5: Schedule and Send Your Bulk SMS Campaign

Enter the task name, select your contact list and SMS template, then set the send date and time. Timing matters: promotional messages tend to perform better during peak shopping hours, while reminders should go out close to the relevant event.

Step 6: Preview, Test, and Check Your Campaign

Review the fully rendered message before sending to the complete list. A template can look correct while still producing broken links, blank fields, or extra SMS segments after real customer data is inserted.

• Confirm that every recipient has valid consent and that suppressed or opted-out contacts are excluded.
• Map each placeholder to the correct data column and define a safe fallback for missing values.
• Preview short and long values, including long names, order numbers, and localized text.
• Test every link, discount code, date, time zone, and opt-out instruction.
• Check the final message encoding and segment count after variables are filled.
• Send a test to internal devices before scheduling the complete campaign.

When the test is correct, launch the campaign and monitor the results. Depending on the campaign and platform, useful checks can include delivery and failure rates, tracked link clicks, attributed conversions, replies, and opt-outs. Compare results by audience segment and message version so the next campaign is based on observed behavior rather than assumptions.

Common Personalized SMS Use Cases and Examples

The following covers the most common scenarios where personalized SMS delivers results — along with ready-to-use templates for each.

Building Customer Relationships

Birthday messages, loyalty milestones, and anniversary thank-you notes create moments of genuine connection. Even when sent in bulk, these messages feel personal — because the timing and content are specific to the individual.

New Product Launches

When a new product arrives, notify customers who have previously purchased or browsed in the same category. This makes the message more relevant than a general announcement sent to the full list.

Promotions and Offers

Personalized discount codes, early-access invitations, and VIP offers can reference the recipient's loyalty status or purchase history. Use those details only when they help explain why the offer is relevant.

Transactional Updates

Order confirmations, shipping notifications, and delivery alerts are natural candidates for personalization because recipients need information about a specific transaction. Details such as an order number, product name, and delivery date make the update useful.

Abandoned Cart Recovery

An abandoned-cart message can remind a shopper about a specific product and provide a direct route back to checkout. Set timing according to the customer's consent, expectations, time zone, and campaign policy rather than applying one schedule to every audience.

Event and Appointment Reminders

Appointment and event reminders should arrive early enough for the recipient to act. Include the specific time, location, and any preparation needed, and choose the lead time that fits the event and audience.

Personalized Recommendations

Post-purchase recommendation messages can introduce a relevant accessory, refill, or related product. Base the recommendation on a clear purchase relationship and avoid using sensitive or unexpected data.

How to Write Effective Personalized Text Messages?

Understand Your Audience: Use the data you have collected to understand what your customers actually want. Consider the products they commonly buy, their previous orders, behavioral signals, and stated interests. The better your understanding of each segment, the more relevant your messages become — and relevance is what drives both opens and conversions.

Go Beyond the Name: Inserting a first name is the baseline. More useful personalization can reference something specific, such as a product the person viewed, a category they frequently buy from, or a time-sensitive offer tied to their location. Use only data the recipient reasonably expects the business to use.

Check Length After Personalization: A single GSM-7 SMS segment can contain up to 160 characters, while UCS-2 text can contain up to 70. Longer messages use concatenated segments with lower per-segment limits. Variables, emoji, smart punctuation, and non-Latin scripts can change the encoding and segment count, so preview the fully rendered message rather than checking only the template.

Add Genuine Value: Every message should give the recipient a clear reason to act. A discount, an exclusive offer, a useful update, a time-sensitive reminder. If the message provides no value, it becomes noise — and repeated noise drives opt-outs.

FAQs About Custom SMS

1 What is a custom SMS sender, and how do I get one?

A custom SMS sender — also called an SMS Sender ID — is the name or number that appears in a recipient's inbox as the message source. Businesses use either an alphanumeric ID (a branded name like "YourBrand") or a numeric virtual number, depending on the target country and whether two-way messaging is needed. You obtain a Sender ID through a certified SMS marketing platform, which handles carrier registration and compliance on your behalf. Not all countries support alphanumeric IDs, so platform-level guidance is essential.

2 How to send personalized bulk SMS?

• Pick an SMS platform with dynamic field support for personalization.
• Upload your contact list with details like name, location, or purchase history.
• Create a template using placeholders (e.g., "Hi [Name]!").
• Select your target segment, then send or schedule the campaign.
• Track delivery and performance to optimize future sends.

3 What is the difference between bulk SMS and personalized SMS?

Bulk SMS refers to sending messages to a large group of recipients at once. The messages can be either generic or personalized.

Traditional bulk SMS sends the same content to everyone, while personalized bulk SMS uses dynamic fields such as names, order numbers, or purchase history to customize each message automatically. This allows businesses to combine the efficiency of bulk delivery with the relevance of one-to-one communication.

4 What is the maximum length of a personalized text message?

A single GSM-7 SMS segment supports up to 160 characters, while a single UCS-2 segment supports up to 70. Concatenated messages typically allow 153 GSM-7 or 67 UCS-2 characters per segment because assembly information uses part of each segment. Personalization variables, emoji, smart punctuation, and non-Latin scripts can change the rendered length or encoding, so check every campaign with a segment calculator or the sending platform's preview before launch. See Twilio's SMS character-limit guide for a technical explanation.

Conclusion

Personalized SMS lets businesses adapt one template to each recipient at scale. The goal is not to use as many data fields as possible; it is to make each message timely, accurate, and useful.

Start with valid consent and reliable customer data, choose only the variables the message needs, and test the rendered result before sending. A suitable platform can help manage templates, delivery, sender registration, automation, and reporting across the campaign workflow.

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