Why do carriers have content and spam filters?

When subscribers receive messages they find objectionable, they may file complaints or report the carrier to governing bodies, seek damages, or simply stop being a customer. All of these things reduce the revenue of or increase costs for carriers. Thus, it is in the best interest of carriers to protect their subscribers from what they consider to be objectionable content.

How do carriers filter messages?

There is no standard practice for carrier filtering across all carriers. For some, filtering can range from a simple static list of prohibited terms to advanced machine learning systems that work in real time. Regardless of the system, carriers keep their filtering systems closely guarded secrets. In turn, SendHub cannot say definitively how these systems work or why a particular message was filtered.

Some reason why are;

  • Sending too many messages from a single phone number or alpha sender ID during a time period could cause that phone number or sender ID to be blacklisted.
  • If you are sending high volume of identical messages

How do I know if my messages are being filtered?

SendHub does not always know when a message has been filtered by a carrier. Some carriers falsely report filtered messages as delivered to prevent spammers from reverse engineering filtering systems. In other cases, carriers will tell us that a particular message has been filtered.  You can see your message delivery status and possible error codes under the “Company Usage” option and by selecting “Download Data”.

How does my number get removed off the blacklist?

The blacklists in the US and Canada use a “cooling off” period, which means that most numbers will automatically be removed from the blacklist after a period of time. This period of time varies based on how many messages were blocked by the carrier from this number, and carriers do not share this time period with us.