I want to be able to do transactional single send (password reset) via an API using this endpoint https://developer.salesforce.com/docs/atlas.en-us.mc-apis.meta/mc-apis/sendMessageSingleRecipient.htm. I managed to successfully send a test e-mail providing a unique messageKey, but in the future I want it to be a part of a larger solution and I would like to avoid handling the creation of unique ids on the side of the API using app.
Documentation says: "messageKey: Unique identifier of the definitionUnique identifier used to track message status. Can be automatically created when you create a message or provided as part of the request." Is it correct? How to trigger the automatic creation of the unique identifier? Using the endpoint without a messageKey value returns "MCMS_UTM_Validation_UnknownFieldName: Unrecognized email field name 'recipient'".