An email thread contains all the emails sent between correspondents and is very useful for documentation purposes, allowing peers to keep track of past conversations. However, email threading can be an annoyance when the topic drifts off or when the conversation becomes quite lengthy. Large numbers of replies can become overwhelming considering that users of the flat or linear style, the most commonly used structure, may attach their replies to the most recent post by default, regardless of which post they are actually replying to. This is a significant downside of the linear display mode on any email thread; it can confuse everyone involved in the discussion.
Because of the wide use of email, the use of email threading tools is being promoted by organizations in order to make communication more efficient. Using these tools will greatly increase efficiency by organized emails in such way that redundancy is limited and the readers may be able to focus on the important parts of the email discussions