e-mail address mining tool?

Hello list.

First off all congratulate every one for always sharing their knowledge for
free and for the... well lets get to the point :)
I'm wondering if any one knows a tool that can gather email addresses of the
users inside a domain, from the email server.

For example:

When u connect to a mail server trough telnet
And u enter the commands

Helo
Mail from: xxxx@something.com
Rcpt to: xxxx@something.com
Etc.....

U can see if the address xxxx@something.com is a valid email.
I was thinking in something that uses like a dictionary off names and then
test all off them.

I was wondering if there is such tool so I don't have to reinvent the wheel.

I hope I make mi self clear. 

Best regards

Hugo Vinicius Garcia Razera
Security Consultant


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