Does anyone know if the message record type is supposed to be editable with suitescript? I'm trying to set the externalid field using a UE script afterSubmit. The script is deployed to the message record type but it is supposed to set the externalid of a different record than the one triggering the script. I'm doing this with record.submitFields and have also tried .load > .setValue > .save, both methods give me a 'That record is not editable.' error.

You cannot edit the existing message

Well, that explains everything. Thank you!