How to use the Dynamic Configuration Bean

Hi experts,

im currently doing a file to mail scenario.

i want the name of the input file as the subject of the mail.

i want to establish this using the Dynamic Configuration bean

my first question is:

key.1 read http://sap.com/xi/XI/System/Mail THeaderSUBJECT

value.1 message.messageID

this reads the value of the message ID into the attribute THeaderSUBJECT

but what does this do?

key.1 write http://sap.com/xi/XI/System/Mail THeaderSUBJECT

value.1 message.messageID

when i use this it has no effect atall.

my second question.

I have my input filename in the FileName attribute in Dynamic configuration how can i read it into THeaderSUBJECT attribute.

Appreciate any suggestions.