To configure Outlook 2007, 2010, 2016 accounts to use SMTP authentication under SSL mode take the steps below:-
1. From the Outlook Menu Bar click on Files.
2. Click on Account Settings>Account Settings.
3. Click on "Change...." option.
4. Click on the More Settings… button.
5. Click on the Outgoing Server tab.
6. Check the box for My outgoing server (SMTP) requires authentication.
7. Click on the "Advanced" tab. Mark the "This server requires an encrypted connection (SSL)" option. The incoming server port will be automatically changed to 995.Set the "Outgoing server (SMTP)" port to 587.
Specify "TLS" at the "Use the following type of encrypted connection" setting.
Make your selections under the "Delivery" section on how to treat the messages on the server after they are downloaded on your computer.
8. Click the OK button.
9. Click the Next button.
10. Click the Finish button.