Re: They knew who sent the e-mail - Were they sacked? -- Outlook
That's a good point. It does not seem that implausible to get Outlook to have a data security mode that scans the e-mail addresses, when more than 2 people from external agencies are receiving a file having a popup to point out the bcc field has not been used - check it does not include sensitive personal info - then press confirm.
It'll be just like software license agreements - many will ignore it anyway, but at least you have active and unavoidable control systems that must be intentionally ignored.