With Thunderbird open, choose the “Tools” menu up top and then choose “Account settings…”
In your account settings window, go to the bottom of the list on the left and chose “Outgoing Server SMTP.” Then click the “Edit…” button on the right.
In the SMTP Server window change the Port number to 587.
Under the Security and Authentication section set the Connection Security to "None" and set the Authentication method to "Password, transmitted insecurely".
Type your First Step user name in the “User Name:” field. That's the part of your email address before the “@” symbol. For example, if your email is “firstname.lastname@example.org” your username would be “example1234”.
Click OK, click OK and you should be good to go!