Geovani, you mean to export emails of all your current site users?
If yes, then you can export them from your database.
If you have phpMyAdmin, just go to the table called "ow_base_user">>select all rows>>click "export"
>>once you click "export" new page will be opened>>select the format (for example CSV or .doc)>>click "Go".
All info will be imported to the selected format. For example, if you export to CSV you will be able to open the file with MS Excel, and copy the list of emails from "Email" column.