More than a year ago, a Gmail account A sent a confidential e-mail to another Gmail account B.
Just today, for reasons that we do not understand, A received an automatic "on-vacation" reply from B to this very old e-mail.
There is no doubt that the automatic reply was actually sent today. How could that happen? Is it a known bug from Gmail?
The motivation for this question is the following: B is strongly suspected of illegally disclosing confidential documents to third-parties with malicious intent. Therefore, we fear that B may have forwarded the old email from A to a third party in a way that somehow resulted in an automatic reply being sent to A today. Is it possible? If so, is there any way to find out?