Email addresses only on line From:

Dear Experts,

I am completely new to regular expression, I have PowerGrep software to test. I have full DVD of emails in EML format.

I would like to know what email address are contained on the line From:

When I just search accross all lines of email for something like this
\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,6}\b

it gives me all emails found in eml file.

Can you advice?

Thanks

Vladimir