You can create or make use of existing distribution lists to email groups of people, such as "Approvers" or "Project ABC Members." If there is a selected group of people that certain mails always need to be sent to, you can make use of these distribution lists instead of selecting recipients one by one.
To use an existing distribution list, when creating a mail, select the "Distribution List" button next to the To field. This opens up a dialog where you can choose from Personal (lists that only you can view) or Public distribution lists (lists that are available to the entire organisation.)
Choose a distribution list and click on the Select button. The recipients in the list get added to the mail.