Nemám možnost to teď vyzkoušet...

There are a few methods you can use for this action:

1. If it is a new message, you can remove the attachment by opening the email message, right-clicking the attachment icon and selecting "Delete". This operation will not work once the email has been moved to another folder as the "Delete" option will be grayed out.
2. Open the email, click File/Save As and save the eml file on your Desktop. Then open it there with Notepad or Wordpad and delete all info below the text in the body of the message all the way to the end. Then in Notepad or Wordpad, click File/Save (NOT Save As) and you can then drag and drop it into a local mail folder in Outlook Express.
3. Open the folder with the message(s) from which you would like to delete the attachment. Right click on the message in the message list and chose "Save message(s) to file(s)...". Save the message to your "New mail folder" which is nothing but your mail directory and give the file containing the message the extension ".cnm". A few seconds later you might be informed that new mail had arrived .... Proceed with method "deleting attachments, when mails are still in the new mail folder".