If you enable tail-sampling and send a transaction that do not match any of the policies, then APM Server will reject the transaction with the error "no matching policy". The reason behind this is to avoid sending every single transaction to Elasticsearch due to bad configuration.

We should instead enforce a catch-all/default policy (i.e. just a sample rate, no criteria). When we have a UI we can have a specific section for this policy, and perhaps add a warning if the user sets the default sample rate to something high.