That's really very strange.
Could you please add the following addresses to the form and run the test again:
to recipients add: supportstaff AT tectite DOT com(you'll need to use your AT_MANGLE, of course).
to BCC add: russellr AT tectite DOT com
Some systems include the BCC list when the email is copied to the sender. It's possible your server knows it is sending a copy to you and therefore includes the BCC list.
Does the mail received at woodhavenhoa.com show the BCC list?
Note that FormMail is just operating according to the email standards, but it cannot control what a server does when it accepts the email for delivery. The server can do the wrong thing, and FormMail has no control over that.