The Reply All button sits next to the Reply button. They look almost identical. The consequences are not.
Reply sends your response to the person who sent the email. Reply All sends it to everyone who received the email, including people who were CC'd, people who were BCC'd (they will not receive it, but you did not know they were there), and people who were added to the thread three weeks ago and have since forgotten about it.
When Reply All is correct
- Your response is relevant to everyone on the thread
- You are confirming something that everyone needs to know (a meeting time, a decision, a change)
- You are adding information that changes the situation for all recipients
- The original email explicitly asked everyone to respond
When Reply All is incorrect
- You are saying "thanks" or "sounds good" to a group of forty people
- Your response is only relevant to the sender
- You are asking a clarifying question that only the sender can answer
- You are sharing an opinion that not everyone needs to have
- You are forwarding the email to someone who was not on the original thread
The "thanks" problem
The Reply All "thanks" is the most common unnecessary email in the workplace. Someone sends an update to thirty people. Three people reply all with "thanks." Thirty people receive three emails that contain no information. Ninety emails have been sent. Zero information has been transferred.
If you want to thank someone, reply to them directly. They will appreciate it more. Everyone else will appreciate not receiving it.
The test
Before hitting Reply All, ask: "Does everyone on this thread need to see my response?" If the answer is no, use Reply.
The rule: Reply All is for information that is relevant to everyone. Reply is for everything else. When in doubt, Reply.