Which of these factors can lead to emails being flagged as duplicate spares?

Emails can be flagged as duplicate spares when they contain the same content being sent to different recipients. This is because many email systems monitor content to reduce redundancy and avoid flooding recipients with repeated information. When the content of the emails is identical, regardless of who it's sent to, the system recognizes this pattern and may categorize them as duplicates. This helps streamline communication and ensure users are not overwhelmed with identical information across multiple emails.

In the case of other factors, while they may seem relevant, they do not typically lead to an automatic flagging as duplicates. For instance, different content from the same sender, emails sent at the exact same time, or emails with identical attachments do not raise the same level of concern for duplication since they involve variations in either the content or the context of the messages being sent.