This add on seems to address this problem. i have not used it so I cannot tell you anything about it.

https://addons.mozilla.org/en-US/thunderbird/addon/use-bcc-instead/?src=ss

Thanks Airmail - for the very quick reply. I've had chance to download and test it now and it is certainly better than relying on memory. You can set bcc as the default when sending mail, which is a great start. And it doen't really matter if I forget to change it when I don't want to use bcc. I shall explore further and see if there is a way of using bcc as the default for lists or individuals rather than all. That would be even better.

You can also turn on the address sidebar by pressing <F9>. Then take a mailing list and simply "add to BCC."

Thanks markstetz I've given this a try but it appears to be necessary for each email I send. Which is where I started - I occasionally forget to use bcc. Or am I missing something? Are you suggesting a way of tagging a mailing list to "use bcc by default in future"? If so, I misunderstood your instructions and didn't do it right.

I've used "use bcc instead" for a while now and it works in that every email I send is bcc - no matter what. But I haven't worked out how to turn it off for an individual email (other than by deactivating it altogether, which is rather pointless). Everything gets switched to bcc, whether I want it or not, when I click "send". Which is great if you want it - but I don't. Still need help here guys. Please.

Sorry Jimbo, I got nuthin'.