I work with the internet for many years and get hundreds of emails a
day. My inbox has probably 5k emails since the last time I cleaned it.
I am sure that I don't need most of the emails, but it's really hard
toorganize it, and I do like to keep one email at least from each
contact so I can contact them back if necessary one day.

Is there any program, tool, plugin that would help me identify emails
from email lists like newsletters, or duplicate emails, or emails that
carry the conversation of previous ones so I don't need the original
ones, etc..

Anything that would help me clean my inbox?

Thanks a lot ofr helping!