Thread Detection by Header Analysis
Threads can be detected by analyzing metadata IDs of an email or a chat, while the actual content is ignored.
The metadata IDs are provided in a commonly used standard for Internet messages. Therefore, thread detection by header analysis covers a lot of email formats.
Thread detection by header analysis is always active, although a Administrator can disable its display.
Important: Always review all emails of such a thread. There is no guarantee that email senders manipulated preceding emails that are contained in the thread.
Grayed out Attachments in Threads
If an attachment is grayed out and preceded by a small icon 
, the attachment is either the duplicate of another attachment in the thread or it is the duplicate of another document that is not linked to the thread.
Example
The sender of an email has stored a document on the file system and then added it as an attachment to an email. If both are loaded into Axcelerate 5, the file system document is not part of the email, but it is still detected as a duplicate of the email attachment.