Sometimes you have had to clean your database or your users, but the problem is that you lose some contacts from great interest .
Likewise, if you want to send emails to your visitors who have commented the internal process can be tedious, and it would be better to send them an email through a newsletter system right?  Well, let's see a simple way to export the emails of your commentators so you can have them in a more appropriate and clean format to send them an email or a newsletter, of course with prior consent.  For this we are going to use an SQL command so we will go to the hosting panel and open the application PHPMyAdmin which is the database manager.
 Once inside select your base of data and go to the SQL tab
That's where will execute the following SQL command :
SELECT DISTINCT ] comment_author_email FROM wp_comments ;
Where you will have to substitute the default code prefix (wp_) for the one you use .
In any way it's easy because PHPMyAdmin has a predictive search engine as you type the name of a table
Then press the continue button and it will show you the results:
 You only have to click on the link of Export from the bottom of the list and on the next screen choose the format, for example CSV .
Y exports a super cute list to be used at your will.
Oh, what do you prefer a plugin?
Well, nothing, you learn less but existing exists, it's called Comments Emails and it's very easy to use … and pull, when you have finished using it.