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perl -wne'while(/[\w\.\-]+@[\w\.\-]+\w+/g){print "$&\n"}' emails.txt | sort -u > output.txt

# this one fixes issues with hyphens in name
perl -ne'if(/[\w\.\-\_]+@([\w\-\_]+\.)+[A-Za-z]{2,4}/g){print "$&\n"}' *.txt





http://bytes.com/topic/unix/answers/648158-extract-email-addresses-big-file