It depends on where it should happen online or offline.
There is the option of rules on most payable mailboxes already on the server to filter.
If it does not do the online mailbox you just have to do it through the email retrieval software (Firefox Thunderbird and Outlook etc.). In both cases can only be achieved by diligence.
I have a feeling that he was asking about something completely different :-D
Thank you I should have thought about a coder before.with adequate budget you can hire a freelance coder - easy to find
general purpose software is cheaper but results will be poor especially if the other side fights back and has some level of protection
Thank you mate it s sounds like ways but I have decided to hire a programmer, I m not good enough with this thingsare you looking to harvest from domain/forum or just scarp from specfic pages? if those pages include patterns at end and start e-mails , you can try this tool to filter @ from bulk of text Text Mechanic – Text Manipulation Tools
alternatively linux is good for this
wget -q -r -l 5 -O - http://emails.com/scrap.html | grep -E -o "\b[a-zA-Z0-9.-]+@[a-zA-Z0-9.-]+\.[a-zA-Z0-9.-]+\b"
but for harvesting it's better to hire programmer .