how to get the topic of mail lists that I most interested in?

[hui tang]

hi,all.
    every day, i receive a mass of mail from mail lists. but i only
interested some of them. And i ordered two mail lists. Every day I open
my mailbox , i will received so many email about all of messages. that's
really a hard thing for me to decide which email is what i wanted.
    so, my question is : how can I filter the mail topic i interested
in?