Provides expired transactions for removal from Gateway memory. The expired transactions may be provided as a list of short IDs or as a list of transaction hashes. Since Gateways are not validating nodes, over time they will collect transactions that have been discarded by blockchain network full nodes. This may occur because, for example, the transaction was invalid, double spent, or provided insufficient fees. The bloXroute BDN will occasionally poll its internal blockchain nodes for a list of valid transactions and compare it to its list of tracked transactions. Transactions not found in internal blockchain nodes will be broadcast to the network with the Transaction Cleanup message to permit Gateways to remove these transactions from their memory.