Best Practices for Business SMS Messaging


This document covers Plum Voice’s recommendations for SMS messaging campaigns using Plum products. Topics include background info on the policies and regulations on SMS messaging, why and how messages might be filtered, and what steps to take to avoid filtering of your messages.

Background: Carrier Policies and Industry Regulations

Each wireless provider – AT&T, Verizon, T-Mobile, and so on – sets compliance policies for the types and behavior of traffic permitted on their networks. Provider policies for messaging have evolved rapidly since ten-digit long code (10DLC) was accepted as a number type for business application-to-person (A2P) messaging in 2019.
Industry-wide regulations were set for A2P SMS and MMS messaging by CTIA. This led to providers and other telecom vendors developing their own A2P policies to 1) ensure regulatory compliance on their networks (this often involves A2P 10DLC registration status) and 2) protect their wireless users from unwanted messaging.
A2P messaging may pass through several different providers and vendors to reach a recipient. This means that throughout its journey, a message must be compliant with each provider and vendor A2P policy. Noncompliant messaging risks policy enforcement measures, including message filtering.


How does message filtering happen?

While wireless providers do not disclose their exact tools and mechanisms, machine learning software is widely reported to be used for automatic message filtering. Messaging traffic determined to be unwanted and/or noncompliant with a provider’s A2P policies are at most risk of being filtered.

My business uses A2P messaging to communicate with customers. How can we avoid filtering?

While no 100% guaranteed methods exist – providers and vendors set their A2P policies and filtering systems at will – Plum Voice recommends the following best practices based on CTIA guidance, provider and vendor policy disclosures, and our observations of successful SMS messaging through our vendors.
  • Your SMS messages should be sent only to wireless users who have consented (or opted in) to receive messages from you.
  • Ensure that your messages clearly identify their sender.
  • Ensure that your messages communicate how to opt out of your messaging campaign, with an industry-standard SMS keyword used for opting out (e.g., STOP). See our article for more info on standard SMS keywords.
  • Opt-out instructions should be provided at least once a month. You should also confirm whether recipients want to continue receiving messages at least once every 18 months.
  • Monitor opt-outs and any SMS-related complaints from customers. If you receive high rates of either one, be prepared to adjust your campaign accordingly. High opt-outs and/or complaints increase the risk of message filtering.

Message contents

  • Messages should be free of emojis, unneeded special characters or capital letters, and grammar or spelling issues. These increase filtering risk as some messages with these features have been associated with attempts to evade being identified as unwanted messaging.
  • Links in your messages should be from a domain that you, the message sender, control. The risk of filtering increases from sending links with obfuscated URLs or from shared domains controlled by multiple individuals or entities, whose separate activities could cause a shared domain to be flagged for filtering.
  • Any shortened links should be from a dedicated short domain that you control. Avoid using any shared public URL shorteners, like Bitly’s free links, to generate shortened links for messaging.

CTIA guidance

  • Review CTIA’s guidance for non-consumer A2P messages in its Messaging Principles and Best Practices guidebook. Wireless providers and telecom vendors with A2P policies have derived them from CTIA regulations and recommended practices. Operating within CTIA’s guidance should reduce message filtering risk overall.

Additional resources

SMS Messaging Best Practices - Plum Voice.pdf
A PDF version of this page's guidance.