Do you CC relevant people and reply to all as a standard procedure?

When emailing external parties, it is a good idea to CC the other colleagues within your organization that may have an interest in the email. Some of the benefits of CC'ing others are:

It can save time
Gives the email more credibility if you have CC'd others in your organization
Colleagues may correct your mistakes

Note: Don't cc people unnecessarily - it is another email problem!

Some people might reply only to the sender of the email ('little r'), ignoring the fact that there were other persons included in the original email. Obviously the original sender intended to keep everyone in the loop, so it would be polite to CC everyone included on the original communication ('Reply All').

2021 04 12 11 22 09 — Figure: Good example - 'Reply All' so that everyone is kept in the loop

Exceptions

If the sender requests a 'little r' reply
If not all recipients need to be informed
If the opinions of some recipients do not matter as they are unlikely to disagree
If the original email was to an alias with many subscribers, in general you should not Reply All

What if the other person drops relevant people?

Sometimes the other person will 'little r' instead of 'Reply All' by mistake. This can be problematic as those dropped off the loop are needed as part of the decision making.

If you are still on the loop, you should reply to the thread as soon as possible, adding back all those dropped from the loop.