This article will give you a step by step guide on how to turn on SMTP authentication on your account in Mozilla Thunderbird.
1) Open Thunderbird.
2) Click “Tools” and then select “Account Settings”
3) Click “Outgoing Server (SMTP)”
4) Select the SMTP server you want to configure and then click “Edit”
5) Check the “Use name and password” box and fill in your full user name in the space for User Name
6) Click OK
This concludes how to turn on SMTP authentication on Thunderbird