The yarn utilities package contains a very useful program called,
editfold.exe. Basically it reads a folder, including inbox, and replaces
the binary chracters that separate each message with a single
message-separating character, ^S (control-s). Then you can edit the file
with any text editor. After you change the file, editfold will change
the file back to a yarn folder by replacing each instance of ^S with the
appropriate new binary characters.
Thus, to change the subject line in some messages, you can use a
batch file like this:
-----------------------Begin Change.bat-------------------------
editfold %1 %1
edit.com %1
editfold %1 %1 /F
----------------------End Change.bat-------------------------
Now run, change.bat inbox, and inbox will come up within your favorite
editor (for instance, edit.com). Use a find command to go to each Subject:
line and change the line as you want to. After you quit the editor, the
your work will be reconverted to a yarn folder.
Yarn does lack the common mail client functiion, of letting you edit
messages that you have saved to a folder. And it is not easy to simulate
this edit functiion from within yarn, because yarn gets very unhappy when
you change a folder from the command shell, while it is running and
processing that folder.