Considering your original question, I wonder why do you need a program to extract emails from webpages. This is email-marketing oriented need. You were just looking to extract emails from your files and letters you received.

Anyway, I made a little search and here is my answer for what you are asking for,

There is a good free program, Vodamail Email Extractor Free Edition 8.1
download from here:
This program is specialized for extracting emails from web pages, so you cannot use it for files and folders on your computer. However, it allows you to import a list from a file so you may use it to eliminate duplicates. So say you used another program to extract emails from files and folder, you can use the output file with Vodamail Email Extractor by importing it

So, the complete free solution is:
- use Shark Email Extractor for files and folders
- use Vodamail Email Extractor Free Edition 8.1 for web pages
- combine the capabilities of the two programs by importing Shark Email Extractor output to Vodamail Email Extractor

Note: Although it says at the download page “Vodamail Email Extractor”, when you download it you’ll see it as “Realva Email Extractor”. (Realva is the publisher)

And actually, on another download site it is called Realva Email Extractor 8.1