Thunderbird : Potentially executable content

Error Message:
An error occurred while sending mail. The mail server responded: Potentially executable content. If you meant to send this file then please package it up as a zip and try again.
Forward Inline or As Attachment by Default
To change whether Mozilla Thunderbird inserts the forwarded message as an attachment or inline in the new email:

1. Select Tools Options... (or Thunderbird Preferences...) from the menu.
2. Go to the Composition category.
3. Make sure you're on the General tab.
4. Choose Inline or As Attachment under Forward messages:.
5. Close the preferences window.