SMS best practice

Angel Cheung
Angel Cheung
  • Updated

SMS is a highly effective method of conversing with your customers, but there are a few things to bear in mind.


Quick links:

Understand the legal obligations of using SMS

Start with your data

Don't be just a number!

Keep your messaging engaging and concise

Be aware of how non-GSM characters impact your character limit

Keep your messaging relevant and valuable to your customers

Limit your CTA to one or two options

Keep inbound responses unique


Understand the legal obligations of using SMS

It is important to understand the obligations outlined in the SPAM Act 2003 under Australian Law.

This includes only sending marketing messages to people who have express or inferred permission to receive them, but also:

  • Identifying yourself as the sender within the SMS
  • Providing an easy way for the recipient to unsubscribe from future marketing SMS eg. To unsubscribe from future offers, replay back with 'UNSUBSCRIBE' or 'STOP'

For further information on the SPAM Act 2003, please visit the ACMA site here.

Ensure you are capturing and referring to your customers' communication preferences when sending out SMS, and always have a clear path for them to opt out if they wish.


Start with your data

Pendula is directly connected to your data source.

Keep your data source clean and up to date to make the most of any SMS communication.

This includes ensuring that:

  • You maintain an accurate record of mobile phone numbers and communication preferences, stored consistently across your contact records

  • You avoid duplicate contact records with the same mobile phone number, to prevent the same contacts being included in communications twice

  • Mobile phone number values are entered in international format ( +61 etc) and don't contain any additional characters such as text or extra numbers

Why do mobile phone numbers need to be stored in international format?

When a recipient replies to one of your messages, it's received by Pendula in this format (we support SMS from all over the world).

Therefore, for Pendula to match this message back to the correct contact record in your data source they need to be stored in this format.


Don't be just a number!

As mentioned above, you are obligated to identify yourself as the sender within your SMS.

Furthermore, the last thing you want after sending out an SMS to a large number of customers is have recipients respond back with "Who is this?".

Ensure you include your business or company name so it is clear who you are and why you are contacting them.

The mobile phone number your SMS are sent from is unique to your business and will not change. You might like to suggest to your customers that they save this number or add it to their contact list for future communication.


Keep your messaging engaging and concise

The most effective SMS content is relevant, interesting and easily understood. It's designed for sending short messages which are rapidly delivered, with a high read and response rate.

Hence the name Short Messaging Service!

Using only standard or GSM characters, you can send up to 160 characters in one SMS. Anything over this number is sent as separate segments, which are stitched together by a recipient's smartphone into what appears as one message.

This is called concatenation.

Once you send more than one segment, your character limit reduces to 153 characters per segment as the message needs to contain invisible headers to denote that the segments should be stitched together.

The standard character set for SMS are GSM-7 characters, which include letters of the English alphabet, numbers, and common punctuation marks or symbols such as !,'@%$=.?/().

There are some GSM characters such as { and which take up two characters, and are known as extended alphabet characters.

Most smartphones and mobile networks support concatenation and will rebuild messages up to a certain number of characters, however this is dependent on the mobile carrier. If a message has too many characters then it will fail to be delivered.

We generally recommend limiting your messages to under 750 characters (or less than 6 segments) to ensure successful message delivery to all recipients.

Keeping your SMS content within the character limit not only ensures it is supported across all mobile devices but also provides a better experience to your customers.


Be aware of how non-GSM characters impact your character limit

Remember how we mentioned character limits above?

Things get a little more interesting once you introduce non-GSM characters to your SMS.

Non-GSM characters consist of any characters with a different encoding to the standard character set for SMS.

Emojis and eastern language scripts which require a far broader array of characters are good examples of non-GSM characters, however many popular text editors also don't support GSM encoding and use a different encoding instead.

Pendula helps you identify when a non-GSM character is introduced to your intended messaging.

The moment a non-GSM character is introduced to an SMS, the initial character limit drops to 70 characters per SMS rather 160 as it has to be sent with a different encoding.

Most emojis take up two characters, however newer ones can take up to 4.

Messages sent with non-GSM characters can also be concatenated, once you send more than one non-GSM segment, your character limit reduces to 64 characters per segment.

That's not to say you shouldn't use emojis or other characters when appropriate, just bear in mind it will increase your message segments, so use them wisely!


Keep your messaging relevant and valuable to your customers

Customers don't want to be spammed with irrelevant messages.

Use merge fields to personalise the contents of your SMS for each recipient, and reference the right information in your data source to only target contacts who will benefit from your messaging.

By providing real value to your customers via SMS, they are less likely to view your communications as unwanted noise, or worse, as spam.

Merge fields are placeholders that are replaced with the literal values relevant to each contact that Pendula sends a communication to, for example First Name or Start Time. See Personalising messages using mergefields for more information.


Limit your CTA to one or two options

Ensure your call to action is clear and straightforward, so recipients aren't confused on how they are supposed to respond. Providing too many different reply options increases the margin for error and generally makes for a worse experience.

If there is a lot of information you wish to capture via SMS, consider breaking this up over a series of messages with a question and answer approach for a seamless and easy to follow conversation.


Keep inbound responses unique

Unlike other forms of communication such as email, the only way to understand the context of a reply sent via SMS is from:

  • the mobile phone number that it was sent from

  • the contents of the message itself

Pendula enables you to easily automate SMS conversations by defining expected responses to your outbound messages, if a reply exactly matches one of these responses then you can have a series of pre-configured actions or process which take place.

It's important however, to keep these expected responses unique to one type of message you are sending.

For example if you send two different offers out via SMS to the same contact, both of which are expecting a response of YES then it's not going to be obvious which offer the recipient is responding back to if they do.

For this reason, avoid any cross-over when automating different responses across your messaging and avoid defining expected keywords or phrases which might be commonly used in everyday correspondence via SMS between your business and recipients of the same messaging.