Exclude default fields from the CSV export

exclude-defaults-fields.php

<?php

add_filter( 'cf7_storage_csv_columns', function( $rows ) {	
	 // Specify the field names you wish to remove
	$unset_fields = array(
		'mail-date',
		'mail-from',
		'mail-to',
		'mail-subject',
		'mail-body',
		'mail-attachments',
		'mail-from-name',
		'entry-id',
		'entry-url',
		'http-referer',
		'http-user-agent',
		'http-remote-addr',
		'field-name', // use field-YOURFIELDNAME for all custom fields
	);

	foreach ( $rows as &$row ) {
		foreach ( $unset_fields as $field_name ) {
			if ( isset( $row[ $field_name ] ) ) {
				unset( $row[ $field_name ] );	 
			}
		}
	}

	return $rows;
} );