Dynamic filename without mapping in AS2 receiver

Hello All,

I have a bypass scenario with AS2 channel as the receiver. The receiving system wants a dymanic name of the file each time.
So I have used DynamicConfiguration bean and I am writing dynamic filename with property message.messageID  to generate the unique filename, the filename comes as 16 character message ID. But now the issue is that the end user wants the filename as <unique name>.txt

I am unable to concat / append two module properties. Is there any standard way to achieve this apart from writing Adapter module

I don't have mapping, so dynamic UDF wont help.

Thanks,

Pragya