Spam filters?

What's the best way to check what might be causing my mail to end up in spam filters? According to this search I'm not blacklisted:

http://www.mxtoolbox.com/SuperTool.aspx?action=blacklist%3a80.68.89.15

but I've been finding it pretty difficult to reach people lately, and starting to think some sort of spam filtering might be responsible. Any ideas?

It's the end of the world as we know it

The technical term for a risk that could destroy the whole future of humanity is an "existential risk".

Wikipedia on existential risk

Nick Bostrom: "Our approach to existential risks cannot be one of trial-and-error. There is no opportunity to learn from errors."

Eliezer Yudkowsky, Cognitive biases potentially affecting judgment of global risks [PDF]

Google search

Do you worry about the end of the world?