Depending on the program used, a BCC (Blind Carbon Copy) can be sent to one who is NOT IDENTIFIED as an addressee.

When you send to a large number of people, everyone to whom you Copy (CC) the mail has their name and email address shown on the email received by every other person on the list.

It's a common, and in fact recommended, method, to send to ONE recipient, with all others on the list as "BCC" addressees, to avoid revealing recipeints' addresses to others.

In your case, the 3 addressees shown at the CC line may be other officers of the club, or others with "published addresses" for whom it's appropriate to have their addresses shown, while you got a BCC that doesn't show others who got the same message.

John