Please post a screenshot of your main Thunderbird window when this happens. https://support.mozilla.org/kb/how-do-i-create-screenshot-my-problem

Here is a screenshot of the firefox page that is brought up when I start thunderbird.

Again, I do not want, nor do I need twitter in my email.

How do I kill this "launch" of twitter?

When asked to post a screenshot of your main Thunderbird window, why are you posting a screenshot of Firefox?

Because when I launch thunderbird, this is what happens!

Again, I do not want, nor do I care to have twitter in my email, so why is thunderbird launching that firefox screen dealing with twitter??

This is a very old bug https://bugzilla.mozilla.org/show_bug.cgi?id=524281

Do you have any RSS feeds? or mail from folk that include a twitter icon in their signature. Generally it is not an issue in mail as remote images are turned off. but turning them on is an invitation to this bug.

Basically a remote image is not an image in this instance, it is a script part of twitters global spying on everyone, even those that do not have an account. Facebook does something similar.

Both get to log your visit or every web page displaying their little image and them place that information with your profile if you actually have an account. Or match it to other data sources so they can identify the individual. That s the true cost of twitter and facebook.

Basically attempts to fetch the image fire a script that loads the transparent single pixel tracking image in your browser because Thunderbird is not your default browser for it to be injected into.