Use mail merge

Use your Outlook address book and mail merge to send a bulk message. 

1. One the left of the Outlook window, select   People or press Ctrl+3

2. On the Home tab, select Mail Merge.
   If you don't see Mail Merge, select the ellipsis (), and choose Mail Merge. 

3. Choose the options you want, and then select OK to open a Word document to craft a personalized letter.

4. In Word, select Finish & Merge > Send Email Messages to send the letter to your set of contacts.

For more info, see Use Outlook contacts as a data source for a mail merge.