I need to email 300+ people how do I set up contact where I dont have to insert each time?

I run a business that I would like to email listing and photos to 300 plus contacts. I have inserted all my email addresses, and put each one in the same contact list. Can we set this up so that each time I dont have to insert checks by all 300 names? I will be sending emails to the same contacts each time.

I need to email 300+ people how do I set up contact where I dont have to insert each time?
In the very bottom of the list, there is an option to "Check All". If you click on that, a check mark will go into all names. Go to the top and click on "Insert Checked Contacts".