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The Dark Side of SMS Whitelisting

What is an instance where positive does not equal good?

This is not a riddle – we are honestly asking!

Most of us are hardwired to think that something positive generally equals good, so if you weren’t able to come up with an answer off the top of your head, by the time you finish reading this article, you will have learned about a phenomenon in SMS which presents as positive but can be quite the opposite.

We are, of course, talking about whitelisting.

The Upsides and Downsides of Whitelisting

Though from the title of this article, it is obvious we will point out the negative side of whitelisting, let’s talk about its upside first.

Whitelisting is a common practice in the SMS industry where a trusted list of phone numbers or sender IDs is created to ensure that messages from those sources are not blocked or filtered as spam by mobile carriers. In this sense, whitelisting can be quite beneficial to ensure that business using legitimate content are able to reach their recipients with no issues.

As good a practice this can be, the possibility of dedicating a route based on phone numbers and/or content brought about a shady practice which now occurs in SMS testing. With the rising trend of testing SMS for Fake DLRs, SMS vendors who were generating them faced an issue; their customers started figuring out when they would receive a Fake Delivery Response and they would complain. This was, of course, bad news for their business as they could no longer keep the façade of high quality while still earning high margin.

Their solution? Whitelisting!

Whitelisting in SMS Testing

As SMS testing became a common practice in recent years, SMS route vendors, who wanted to continue using shady practices to earn extra profit, started to figure out which phone numbers and content were being used for quality checks and started setting up special routing for them. This way, all messages sent with a specific content, or to a specific number would always be delivered.

Simply put – they would send test messages via the routes that always deliver for the purpose of falsifying your SMS test results, making them positive to lull you into a false sense of security, while in production delivery issues continue to happen.

Now, I can guess what you’re thinking: 

How can I then rely on SMS testing if my SMS vendors have a way to bypass my checks?

Tips that will Help you Avoid Whitelisting

With our years of experience in SMS testing and close to 50 million tests conducted on our SMS Testing Platform, through this article, we wished to share some tips and best practices that can help you ensure your investment is SMS testing pays off.

Our Tips:

  1. Not all positive SMS test results point to whitelisting; this is very important to remember. Whitelisting can be ascertained only when you always receive positive test results with specific numbers or content. To counter this, our advice is to frequently test with multiple numbers and different content.
  2. Use a reliable SMS Testing Tool that takes good care of their testing numbers. TelQ makes sure our coverage is frequently revised and our numbers replaced. We also offer templates which look like live messages to prevent whitelisting based on words such as “test”, “testing”, etc.
  3. Never escalate test numbers to your SMS vendors. If you let your vendor know what number you used to test with, or what number had failed delivery, they will whitelist it. This will render that test number useless for quality checks.
  4. Create content as similar to your live traffic as possible. TelQ created a dynamic test ID text which makes your testing code modifiable and helps blend it in your message.

These simple tips for testing your SMS will help you:

  • make sure your results are not tampered with;
  • real-world conditions are tested;
  • delivery issues are identified and fixed.


Now that you know the answer to our initial question, we invite to take a closer look at your SMS tests and analytics. Is there something unusual that you notice? Perhaps a spike of positive delivery in the last couple of months? Does your new SMS testing platform give you only positive results? If so, now you know that the answer is whitelisting!

If you want to combat this harmful practice, we got you covered!
Reach out to our team and let’s discuss solutions together.

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