Easy!

1. Click Compose to open a Compose page.
2. Now, click To:. This opens your Address Book in a sub-window.
3. Beside any names to which you’d like to send the email, check either the To:, Cc: or Bcc: box. (Bcc: sends the email to someone, but their name will not appear in the address block of the Sent mail.)
4. When you’ve checked all the contacts you wish to add, click Insert Checked Contacts.

That’s it. Now comes the hard part. What are you going to say? :o)

Will you be emailing this group again? If so, it's a good idea to create a category for the group, so that next time, you can select all these contacts in just one click.

Note: If you’re adding more than ten contacts and having difficulty sending the message, please try breaking up the group of recipients into groups of ten.