Hi, not sure from your description if you’ve already done these steps: usually you define a flat file schema for your txt file. This will defile how the flat file gets transformed to XML. Then create a pipeline with the flat file disassembler component in it that references the flat file schema you created. If the output of the flat fiel schema is not exactly in the XML format you want you can create your destination schema and create a map between the flat file schema and the destination xml schema. Tthen deploy the solution and on your receive port select the pipeline you created and not the pass thru receive one. On the send port add a filter under the Filters tab on the send port configuration so that it filters on the receive port name (BTS.ReceivePortName = your receive port name), or on the flat file message type.
Hope this helps!
Thiago Almeida
http://connectedthoughts.wordpress.com