> I'm not moving the goalposts; you guys are talking about the NFL game's goalposts; I'm talking about the FIFA world cup game goalposts.
Analogously, the issue would be out of bounds then, as the issues are distinct, and so a failure mode that discloses the existence of an email account is not a failure you can lay at the feet of any particular provider of email accounts, but is partly an implementation detail of how different email providers respond to emails to nonexistent addresses. That particular failure (disclosure of the existence of an email address) and any potential solution is considered out of the scope of the problem in the thread (disclosure of the opening of an HTML email due to loading tracking pixels).
Analogously, the issue would be out of bounds then, as the issues are distinct, and so a failure mode that discloses the existence of an email account is not a failure you can lay at the feet of any particular provider of email accounts, but is partly an implementation detail of how different email providers respond to emails to nonexistent addresses. That particular failure (disclosure of the existence of an email address) and any potential solution is considered out of the scope of the problem in the thread (disclosure of the opening of an HTML email due to loading tracking pixels).