A.Use BCC instead of CC, and only use CC when necessary

It is always preferable to use BCC (Blind Carbon Copy) instead of TO and CC fields for large email distribution, especially when addressing a group of recipients who do not need to communicate with one another. This is crucial for several reasons, especially from a security perspective:

• Privacy Protection: BCC hides the email addresses of all recipients, ensuring their privacy. This prevents unauthorized access to personal email addresses.
• Reduced Risk of Spam: Exposing email addresses in the TO or CC fields can lead to those addresses being harvested for spam or phishing attacks.
• Preventing Reply-All Storms: Using BCC prevents recipients from accidentally or maliciously replying to all, which can lead to unnecessary email traffic and potential information leaks.
• Centralized Communication: BCC ensures that replies are directed only to the sender, maintaining a controlled and centralized communication flow.

Make sure you always have the BCC field open in Outlook. Click on ‘Options’ and then select ‘Show Bcc’ to open the BCC field.

B. Use mailing lists

Colleagues may also consider using mailing lists if necessary, particularly in the following situations:  

• Regular Communication: If you need to send updates or information to a large group of recipients regularly, using a mailing list is more convenient than using CC. 
• Allow Unsubscription: With proper mailing list configuration, recipients can opt out of the mailing list if they no longer wish to receive emails. 
• Privacy: A mailing list ensures that everyone receives the same message at the same time, reducing the chance of miscommunication. 

To avoid abuse to the mailing list, please consider configure the mailing list to be sent by authorized person only (please refer to this link for details).