Messages identified as SPAM will be rejected and error code 255 returned. Sinch continuously monitors for senders with a high number of SPAM rejections. If the SPAM message content is not resolved, the TFN is subject to blocking and deprovisioning.
Sinch Toll-Free Sender Verification ensures better deliverability for messages from your toll-free number (TFN). TFNs that are not verified are subject to rate limits and blocking towards US and Canadian carriers.