Pre-selected vs. Un-selected Customization Tool

I am working on a team messaging tool. Users have been asking to send to just part of the team. (ie. If a team had 40 members and I wanted to just send something to 18 of them)

The proposed solution would be a slide out where the members would be listed out.

My question is: Do you think it makes sense to have all team members selected in the initial state (option 1) or have everyone deselected by default (option 2)?

My original thought was that you are starting out with the "complete" list so everyone should be selected by default.