What Is the Difference between a Network-Enforced Minimum Fee and a Node’s Relay Policy?

A network-enforced minimum fee is a rule written into the core protocol that makes any transaction below that rate invalid and unconfirmable by any miner. A node's relay policy, however, is a non-consensus rule set by individual node operators for which transactions they will accept into their mempool and broadcast to other peers.

While a transaction may be technically valid (meeting the network-enforced minimum), a node's relay policy may reject it if the fee is too low to prevent resource drain. The relay policy is a defense against spam, while the network minimum is a fundamental validity check.