"Reply All" is an email function that allows recipients to respond to all individuals included in the original message. This feature is useful for group discussions, ensuring that everyone involved can see the responses and stay informed. However, using "Reply All" can sometimes lead to unnecessary clutter in inboxes, especially if the conversation is not relevant to all recipients. It's important to consider whether everyone needs to receive the response before using this option, as it can overwhelm inboxes and distract from important messages.