STARTTLS is a way to take an existing insecure connection and upgrade it to a secure connection using SSL/TLS.

To change your existing connection to TLS in your Outlook, please use the follow guide.

Kindly note that this guide uses Outlook 2007 and newer Outlook version, the location of the mentioned function may be different.

1. Launch your Outlook
2. Click on "Tools" > "Account Settings"

3. Under "Email" tab, double click on the email address that you need to make the change.

Before proceeding the following, kindly note down of the current working value for the "Outgoing server (SMTP)" and the down drop selection for "Use the following types of encrypted connection". This is so that in the event there is any issue afterwards, you may revert back to the working value and settings.

4. Click on "Advanced" tab. Under "Outgoing Server" > "Use the following types of encrypted connection" click on the drop down and select "TLS".
   Outgoing port able to use with TLS are: 25 and 587.

5. Please also ensure under "Outgoing Server" tab, the checkbox for "My outgoing server (SMTP) requires authentication" is selected.

6. Click on "OK" and click on "Test Account Settings" and it will proceed to test the settings you set. If all goes well, it will show all "Complete" under the "Status" section. Then you can proceed to close Windows you opened.