Any output which is produced from an integration in XIB and stored as a file afterwards (using file connector or ftp connector) gets a file name which is closely related to the logger ID.
I would like to know what are the facilities for giving an output file of an integration a certain name of the users choice? I want a solution when using Message builder and DML

We can set the output filename to any name of our choice : we just need to update the attributes RemoteFileName to the name you want to give and Use_RemoteFileName to 1

MBC : check the sample CORE_ROOT/example/hierch/procmbc_examplecreator.s4 to check how to modify an attribute

DML : override the attributes in a Map Broker as follow
setStringAttribute("FTPSendMethodOverride ", "RemoteFileName", "out.txt")
setAttribute("FTPSendMethodOverride ", "Use_RemoteFileName", 1)