warnings[] = 'The export cannot be used for backup and restore. Read more.'; ?>

init(); ?>
select('separator', array(';' => 'Semicolon', ',' => 'Comma', 'tab' => 'Tabulation')); ?>

Try to change the separator if Excel does not recognize the columns.

lists_select('list', __('All', 'newsletter')); ?>

button('export', __('Export', 'newsletter')); ?>