Depending on your workspace configuration, Standard users are able to create chats with up to 100 users, so that users can't inadvertently spam 1000s of colleagues across the business.

There are, however, instances where an admin user will need to address more than 100 people such as:

If you have the "Create large conversations" permission then you are able to create large conversations with over 100 participants.

If you feel you should have this permission, please contact your internal Yapster Administrator, who will be able to give this to you.