How To Send Group Emails In Gmail

You can send a group email in Gmail if you need to email the same message to several people.  Group emails are effective in saving  time and resources.
To send a group email in Gmail, simply go to the compose page and enter the email addresses of the recipients email addresses separated by commas in the To: field. (or Cc and Bcc fields)

As you type each address, you may see an auto-complete suggestion that you can click to add that address.

The main disadvantage to this is that you have to know their email addresses or names to do this.  If you have a group of people you email frequently,  you can create a contact group from contacts.google.com When you want to email the group, simply start typing the name of the group and click on it in the suggestions.