This message is sent by an account servicer (account servicing institution) to an account owner or its designated agent. The account servicer may be a local agent (sub-custodian) acting on behalf of their global custodian customer, or a custodian acting on behalf of an investment management institution or a broker/dealer.
This message is used to advise the account owner that a counterparty has alleged an instruction against account owner's account at the account servicer and the account servicer could not find the corresponding instruction of the account owner (the function of the message is NEWM).