If you haven’t changed defaults in Site Settings\User Preferences then this is not likely an issue that caused your mass emailing
Under the Admin.sidebar, all site settings, user preferences you can set a variety of defaults like you would in your own Preferences on your profile and have the apply to all users in the admin area.
If you have created groups you can also set member defaults for category and tag notifications.
Educating your members on notification types might also be an ideal.
What Jay said though about limiting number of daily emails per user is your best option to have best control.
Same area “All site settings” search term ‘max email’ it is under email section. But here is a SS for ease
