[Mailman-Users] Delete message in large mbox

[Odieresis [Gmail]]

Hi,

I need to delete a message from the archive. I read in some post I have 
to open mbox file of the list and manually remove the message as in 
source code. Then to rebuild the archive it's necessary to backup the 
archive folder and leave it blank.

Now I have a large mbox of MB 200. Can you tell me how I can handle such 
a file direct in shell access or downloading and uploading it?

Thank you for your time,

Francesco