The useful starting point
A routine coordination message may need a contact name but not an address, account number or private document. Copying an entire earlier thread can also bring unrelated information into a new audience. Review the content, not just the newest paragraph.
A small step to try
List the details necessary for the recipient’s task and remove unrelated material. Check attachments and quoted history before sending. Keep obligations and organisational policy with the responsible people; do not invent a universal retention or disclosure rule. FTC business guidance is a U.S. context resource, while your actual handling decision depends on the service, purpose and applicable requirements.