One other thing, about half the time Siri asking, "who do you want to speak to on Face Time?" And "Face Time" at top of Siri window.

I've never come across any person who can verify Thunderbird email client is effecting Siri. But the MAC forums are littered with Siri and Face Time auto launching queries. eg: it seems to turn on when using headphones. or seems to initiate when phone is close to computer and connected to wifi. check settings and preferences>Siri, if you have a keyboard command enabled which you commonly press.

But best place to ask is in the MAC forums as more people can offer specific help regarding MAC.

Indeed this seems highly unlikely.

dpauker, did you determine the cause?