SMS Best Practices

VanillaSoft’s SMS feature is a powerful person-to-person messaging tool that allows callers to interact with contacts and leads on a personal level. In an effort to fight spam and abuse, cell phone carriers - both the sending carriers and the receiving carriers - have increased regulations and monitoring practices to ensure that person-to-person SMS messaging is used as intended.

Most importantly, person-to-person SMS (such as what VanillaSoft offers) is intended to be used for conversations - not for marketing or unsolicited messaging. As of 2018, carriers are cracking down on messages perceived as violating the intent of person-to-person SMS. The side-effect of this crackdown is that sometimes legitimate messages may be blocked. VanillaSoft has several recommendations to help you remain compliant with carrier policies. Note that this guide assumes that your messaging already follows TCPA compliance guidelines. The following are some suggestions to help ensure that your SMS messages get delivered:

Velocity Thresholds and Throttles

Velocity refers to the speed and frequency at which SMS messages are sent. Below are suggestions on how many messages can be sent before SMS may be disabled on your phone number. Note that these are guidelines only, and can vary depending on the recipient’s SMS carrier.

  • 60 messages per minute from a single originating telephone number
  • 125 messages per 60 minutes from a single originating telephone number
  • 1,000 messages per 24 hours from a single originating telephone number

Traffic Balance

Another important metric that is considered by SMS and cellular carriers is the traffic balance. This refers to the balance of incoming and outgoing messages to and from a single number. For example, if you text a Contact three times and only receive one response, you are texting at a 3:1 ratio.

The current industry guidelines call for a ratio close to 1:1, meaning that sending a high volume of non-responsive text messages will raise a red flag for many carriers. Because of this, you should always ensure that your text messages are conversational and focused on engaging with contacts.

Content Filtering & Fingerprinting

Carriers also review the content of each message for keywords/phrases that help to indicate if it could be spam. Some things that may indicate spam are:  a website URL, commonly used words or phrases that have previously been flagged, a recipient reported the message to their carrier, or even that the same message has gone out multiple times with little or no variation. Once the carrier’s filtering system has flagged a message for spam, it “fingerprints” that message, taking several key data points that it compares against all future messaging. This is similar to the logic that’s been applied for years to e-mail spam.

Much like e-mail spam, there is no hard-and-fast rule as to what messages or content might trigger a filter. Furthermore, the strictness of these filters will vary from carrier to carrier, so what’s blocked by one carrier might be allowed with another.

A general rule of thumb is to keep your messages conversational and in line with the intent of person-to-person communication. Sending URLs, marketing material, sales pitches, quotes, etc. is a sure way to get your content filtered.

If your message has been blocked, it does not necessarily mean that your number can no longer send texts. It is often a matter of the content alone being blocked, not your number, though continuing to send blocked content will likely lead to more restrictions being applied.


When a user Is detected as having violated any of the above criteria, their phone number may be blacklisted without notice. Blacklisting can happen from either the sender’s carrier, or the recipient’s carrier, or both. Being blacklisted means that your SMS messages may no longer get sent to, or received by, the contact. Blacklists often last for a period of 30 days, though some may be shorter. Blacklisting generally only occurs after multiple repeated offenses, but it is up to the carrier’s judgment.

Steps to Take

If you discover that you are being filtered for either content or velocity, it’s important to cease texting right away so you can evaluate what may be happening. If the volume & frequency is in line with the velocity thresholds, then the culprit is likely your content.

VanillaSoft’s SMS applies a pre-filter that attempts to catch content and velocity violations before they can reach the carrier. This is a critical step that helps prevent your message from hitting the recipient carrier, which could result in a long-term or even lifetime ban. When you receive a notification stating that your message wasn’t delivered for content or velocity, it’s critical to re-evaluate your SMS habits.

Failure to comply and react to the above could result in your SMS number being blacklisted. Continuing to send messages could extend the time of the blacklisting, even leading to a permanent ban.


SMS is a valuable engagement channel, but it’s important to understand when to use it. Unlike e-mail, the controls are in the hands of the carriers, who have no options for whitelisting or maintaining established business relationships. You can derive tremendous benefits by reaching your audience via SMS as long you follow the guidelines set by the carriers.

The above suggestions are best practices to prevent the accidental flagging of legitimate communications. This is not intended as legal advice, and does not guarantee TCPA compliance.


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