In the realm of research, efficient communication with study subjects through text messaging has become indispensable. However, navigating the intricacies of mobile carrier spam filters has emerged as a critical consideration.

It’s essential to acknowledge that the determination of what constitutes a spam message rests with the mobile carriers, and despite obtaining explicit consent from study participants, research messages are subject to the same filtering standards. While the forthcoming bullet points offer valuable insights to mitigate the risk of messages being flagged as spam, they can’t provide an absolute assurance against such occurrences or the potential blocking of numbers. Like email spam filters, things are always changing as spammers change their game.

These guidelines are designed to empower researchers with strategies to enhance the deliverability of their messages, thereby assisting in maintaining the uninterrupted progression of their projects. While we feel these tips are helpful, they are no guarantee that a message or number won’t get flagged as spam.

Make your text message content personal and conversational, not robotic. “Personal” does not mean you need to add PHI, just more human-like. Text messaging is a conversation, even if your messages are only intended to be one-way, so it’s ok to add more conversational phrasing.

Include the name of the organization

This really depends on your use case, but some clients put the name of the organization. Others use a project name. Both help show that there is an organization behind the messages being sent, one that can be looked up online.

Avoid ALL CAPS messaging, special characters and $ symbols

Non-letters, number characters, etc that don’t look like two people communicating can kick off spam filters. ALL CAPS messages can as well, especially if they involve a call to action with some type of link.

Limit the number of links in your messages to 2 or less

Use only one if you can.

Limit the use of popular URL shorteners

Spammers use bitly, tinyurl and other free link shortening services. While they can be useful, different types of content associated with them may cause issues. Mosio has its own proprietary link shortening system, which we encourage clients to use. 

Unreasonably long links will also trigger spam filters

Avoid sharing ones that look like:


Avoid sending multiple identical messages

“Please take this survey.” is not only bland and provides no context for participants, sending it over and over again may make mobile carriers suspicious.

Send a welcome message on enrollment

Encourage participants to save your texting number in their phone contacts. 

If acceptable with your IRB, be sure to identify the study in the project name so participants know who it is when they receive a text!

Referencing the project name is a great way to help participants feel they are a part of something. Sending an initial welcome message with the project name, encouraging participants to add it to their phone contacts is a great way to initiate high engagement and keep adherence high throughout your communications. 

Place your links in-between words

Surround your links with an explanation of where you’re sending the customer. That way both carriers and customers know you aren’t taking them somewhere dangerous.

Avoid sending “naked links”

Always include that first portion of your link to avoid triggering spam filters.  Mobile carriers care a lot about security and protecting their consumers, so we assume having “https://www.” shows that you link to a secured site and are less likely to be a spammer.

Limit your texts to 160 characters/segments (avoid lengthy text in general)

We understand that longer messages can be useful to deliver helpful information. Mosio will concatenate messages accordingly. But use longer messages sparingly if you can. 

Proofing your texts before you send them is a must

Atypical sentence structure, grammatical errors, and misspellings are the biggest indicator of spam. If your sentences are filled with typos, or sound like they were created by a wonky A.I., carriers will block you.

Offer a way to opt-out

Follow TCPA guidelines, and offer an easy opt-out (“text STOP to stop receiving these messages”) to avoid legal issues.

Register your 10-digit long code number (10DLC)

Mosio handles this for you so you can focus on your research. 

Send text to small lists

Avoid sending a text sent to thousands of subscribers.   Mobile carriers assume that the message is a “pray and spray” message. These types of messages are large, unsolicited advertisements, often detailing some type of coupon or other deal. To prevent the carrier from mistaking your message for spam, send content to small lists. 

Use custom fields

When sending  templated messages to subscribers, use custom fields to make the message unique or personal to the receiver. This makes it read like a person sent it another person (P2P). Not only can this help a message not get marked as spam, it has the potential to be a better form of communication. 

We hope this has been helpful. When in doubt, always test before you go live, on multiple phones and with multiple mobile carriers if you can. Testing with your team can be a great way to test while going through the study participant experience as it relates to your communications.

Happy texting!