Taken from the Clise Etiquette Website:
“The dreaded “Reply all” email response
October 22, 2019
When it comes to using “Reply all,” it’s best to err on the side of not using it, and instead reply directly to the sender. Most of the times the other people on the email list do not need to see your response. Here are some tips for when and when not to use “Reply all” in an email.
Situations when you don’t need to use the “Reply all” response
If you have been ccd on an email it’s rare for the sender to want you to respond to everyone. When a sender puts email addresses in the cc field they are basically giving those ccd folks a “copy” of the email for their information. People in the cc field are not part of the conversation with the sender. They are just being informed of the email. Therefore it’s safe to assume you are not meant to respond to the whole group.
“Reply all” is not necessary in response to congratulations or happy birthday emails for one person. If you want to send your good wishes, do so by emailing just the person being congratulated, not the whole group.
Avoid using “Reply all” in an information-only type email, such as the time or date of a meeting or a report of some sort. If you have a conflict or need more information reply only to the person who sent the email, not the entire group.
Never use “Reply all” to disagree with or correct someone. That is between you and the sender, not the others on the email. It’s a bit like pointing out that someone did something wrong in an in-person meeting. Doing so shames the other person in front of others. If you need to disagree or inform someone of a mistake—do so directly.
“Reply all” is not necessary to state that you received or will take action on an email. Again, that’s between you and the sender and not everyone else.
Nix using “Reply all” to thank the sender. Really, everyone on the email does not want to receive a million “thanks” emails.
Avoid using “Reply all” when the sender is trying to find a date for a group to meet. State your availability to just the sender and let them sort out what does and doesn’t work for the group. For those people who send scheduling emails, make life easier for you and your group by using a scheduling site or app like doodle.com. It makes finding a mutually agreeable time for a group meeting so much easier than back and forth emails.
Situations where “Reply all” is necessary
There are not many times when Reply all is necessary. But there are a few exceptions.
Use “Reply all” if the sender is asking for a group discussion or feedback.
If there are compliance or legal requirements to tracking conversations you might need to use “Reply all.” This should be rare.
“Reply all” might be necessary if the emailed group needs to see your response about your input on a topic.
Other than these very few situations, it is rare you need to use “Reply all,” especially if your email address is in the cc field.”
Taken from the following link:
https://cliseetiquette.com/dreaded-reply-email-response/ and edited for our needs.