A routing delivery is considered successful as long as your route endpoint returns 2xx HTTP status codes. Failed routing for inbound messages are retried 10 times over 7+ hours. The retry policy uses an exponential backoff based on how many times the route has errored. A randomized ±10% jitter is applied to prevent stampeding errors from all retrying at the same time. 
time to next attempt: unsuccessful attempts ^ 4 + rand(±10%)
After 100 consecutive failures, the route is automatically disabled, and all account members will be notified via email.