dynamic filename in mail adapter

Hi,

how can I set the filename of a mail attachment dynamically in a receiver mail adapter (also dynamically configured)?

I had to uncheck the "keep attachment" because of our scenario.

If I check this box I get a .xml file which I can rename with the MessageTransformBean (but not dynamically?) but I get to much files in the mail.

Now I get a .dat file and want to rename it dynamically in e.g. dynamicName.txt.

Can you give me some input how to do that?

Thanks in advance

Dominic