Who among us has not made the mistake of sending a 'broadcast' email to a large number of recipients without using BCC; thereby revealing everyone's email addresses to all?
Use Bcc Instead is a Firefox extension that attempts to prevent this from occurring. It does so by checking each email, upon sending, to see if it is being sent to either non-BCC'ed mailing lists or to more than a user-configured number of recipients who have NOT been BCC'ed. Should this occur, the user is either warned or the email send is prohibited.
I have personally tested this version of the add-on only under Windows XP Pro. I have every reason to expect that this add-on will work on other platforms as well - please let me know what you find.
After installation, this add-on will inspect the recipient list for each email sent. It will count the number of recipients to see how many are NOT being BCC'ed. If that count exceeds a value set by the user in this add-on's options panel or if any recipient is a non-BCC'ed mailing list, this add-on will take action to help prevent the unintended revelation of recipient email addresses.
The action that this add-on takes depends on how the user has configured a second setting in the add-on's options panel. By default, a warning message is displayed giving the user a chance to reconsider the sending of the email. This option can be changed to simply prohibit the sending of the email.
This add-on offers two user-configured options which control its behavior. These can most easily be manipulated via the built-in add-on options dialog. To access this dialog, go to the Tools menu and select 'Add-ons'. You will see a list of installed add-ons and 'Use Bcc Instead' should be in the list. If not, the installation did not succeed. If so, just press the Options button. These options do not require a restart of Thunderbird to take effect.
How to Install in Thunderbird:
1. Right-click the link below and choose "Save Link As..." to download and save the file to your hard disk.
2. In Mozilla Thunderbird, open Add-ons from the Tools menu.
3. Click the Install button, and locate/select the file you downloaded and click "OK".
- Minor improvement, suggested by Eberhard Kuemmerle, to permit the use of ; as well as , when delimiting multiple email addresses on a single line. Please note that while UseBccInstead will permit this, not all versions of TB will permit it. It seems to be in violation of the RFC but supported now anyway due in part to its support in MS Outlook.