1. Open your Thunderbird app

  2. Select Tools at the top of the page, if the Toolbar doesn’t appear at first, press the Alt button on your keyboard and it will appear

  3. Once you have clicked on Tools, click on Account Settings

  4. In the box to the left you will see all emails which you have in your Thunderbird, at the very bottom, click Outgoing Server (SMTP)

  5. You will then see the emails which you have listed, select the email address you want to amend, and click Edit

  6. A box will then pop up with the SMTP Outgoing Server Settings, in that box, change the port number to 587, and the Connection Security to STARTTLS