SMS can be an extraordinarily effective communications channel for marketing, sales, and service. When receiving an SMS, 90% of messages are read within 3 minutes of delivery. But its that last word, delivery, that is somewhat complicated and nuanced.
When sending a text through Prompt.io, we process that message through a Message Network Operator (MNO) such as Twilio, Telnyx, or Bandwidth. The MNOs typically route the messages to the appropriate carrier (ATT, Tmobile, Verizon) which in turn sends to the destination mobile phone.
Understanding Carrier Filtering
At the carrier level, content is often examined algorithmically to determine if the content is appropriate for delivery — this is known as "Carrier Filtering" or "Carrier Blocking." Over time, as SMS volumes and the number of bad actors have increased, the carriers have become much more aggressive in blocking outbound messages. The algorithms used by the carriers are not published and change frequently.
Message filtering can often be triggered by a simplistic list of static keywords or prohibited term. Advanced, adaptive machine learning systems are also employed that have a more dynamic approach.
- Clearly identify your company as the sender.
- Offering clear opt-out language can improve deliverability.
- Avoid generic links and link trackers such as bit.ly — some of the carrier filtering mechanisms very aggressively block link shortened URLs.
Prompt.io offers "First Message" functionality to help facilitate improved deliverability. The first message will always be delivered to a contact immediatetly prior to delivery of the first content delivered to the recipient.
Detecting Deliverability Issues
For messages that are carrier filtered, very often the message will show a Carrier Filter error. In the case of Twilio as the MNO, that error code will show in Prompt.io as error 30007. Note that in some cases, the carriers will actually report a filtered message as delivered — and not report the error code.
Toll-Free Improves Deliverability
Use of toll-free numbers can show an increase in deliverability over use of standard 10-digit local channels, specially for high-volume sends.
MMS, sendiing photos and videos, is a great way to connect and send content. Each carrier and MNO have different file sizes that are supported. Maximizing deliverability of MMS is built in to our platform — the message network operator limits as well as the carrier limitations are utilized to ensure best possible delivery. For video, it is recommended that files are compressed to no more than 500kb which is good for about 15 seconds of video.