Hello,

 

You can set business hours by going to Settings -> Calendar Settings. Here, you can set business hours during the week. For days you're "closed" simply set the time to the same hour. (E.g., 11:00 pm - 11:00 pm). Your "open" hours will be highlighted on your daily/weekly calendar. You can still set up appointments for days/times outside of your business hours, but that's expected as you may want to use one calendar for business and personal appointments.

 

Regarding your mailing list, while it's not recommended to use an "open" mailing list for any reason, you can ban users/domains. Simply go to Mailing Lists, edit the list in question, click on the Banned Users tab and click the New button. Here you can add in a wildcard (e.g., *@domain.ext) to ban users of that domain. Obviously you want to be careful with that as you can ban anyone using that domain as a whole. You can also add in individual addresses as needed.