Can I set up Gmail Auto BCC bcc so that all sent emails are BCC'd?
Yes – that is possible. Short instructions on how to do that are here.
Is it possible to auto CC/BCC based on recipients?
Yes – that is possible. You can setup rules so that BCC will trigger only when sending to certain recipients. Short instructions on how do that are here.
How can I ensure that all emails not sent within a particular domain are automatically BCC'd?
If you wish to BCC all emails not sent within the organization, please select the option “to everyone, but not to” and exclude domain you want, for example “@gmail.com”. So, any email you send to addresses other than the one you’ve excluded (e.g., “@gmail.com”) will have a BCC added to it.
I'm getting error "Please enter at least one valid email address or domain." – what does this mean?
If you see the error message “Please enter at least one valid email address or domain,” it means you haven’t entered the required email address or domain needed to trigger the autobcc feature. This happens when you choose the rule to only these receipts or to everyone, but not to — you must specify which email addresses or domains these rules should apply to. To have autobcc work for every email you send, use the rule to anyone. In other words, of you are looking to BCC or CC all outgoing emails without any particular condition, make sure to select the to anyone option and then you will not need to enter any email address under the rules section. For step-by-step instructions on setting up these rules, please visit the support pages: How to set rules for automatic BCC or CC for Gmail or How to set rules for automatic BCC for all sent emails.