Can I set up default compose address line as "bcc" instead of "To"?

[robertb1]

I'd like to set "bcc" as the line to enter addresses instead of the default "To" line.  I send out a newsletter and I mistakenly added my recipient email addresses into the "To" line so all the email addresses were visible to all the recipients.  I'd like to not repeat that mistake again by making bcc the default option.  Is there some way to do that?

Thanks!