Gray route

An unofficial SMS delivery path that dodges carrier A2P fees, cheaper but heavily filtered and unreliable.

Gray routes push application traffic through channels priced for person-to-person messaging or through interconnects that bypass the destination carrier's commercial agreements. Senders use them to cut costs; carriers respond with filtering that silently drops messages.

For verification, gray routes are the classic reason a code "was sent" but never arrived. Refund-on-timeout policies exist because no provider fully escapes route variance.