code: public function get_members( $current_user_email = NULL, $context = '' ) {
  
  		if ( array_key_exists( 'send_next_group', $this->options[ 'static_options' ] ) ) {
  			$user_addresses = $this->options[ 'static_options' ][ 'send_next_group' ];
  		} else {
  			$meta_key      = $context . '_subscription';
  			$meta_value    = '0';
  			$meta_compare  = '!=';
  			$include_empty = TRUE;
  
  			if ( self::$default_opt_in === FALSE ) {
  				$meta_value    = '1';
  				$meta_compare  = '=';
  				$include_empty = FALSE;
  			}
  
  			$users = $this->get_users_by_meta(
  				$meta_key, $meta_value, $meta_compare, $include_empty
  			);
  
  			$user_addresses = array();
  			if ( ! is_array( $users ) || empty( $users ) ) {
  				return array();
  			}
  
  			foreach ( $users as $user ) {
  				if ( $current_user_email === $user->data->user_email ) {
  					continue;
  				}
  				$user_addresses[] = apply_filters( 'iac_single_email_address', $user->data->user_email );
  			}
  		}
  
  		/**
  		 * Filter the list of user email addresses
  		 *
  		 * @param array $user_addresses
  		 *
  		 * @return array
  		 */
  		return apply_filters( 'iac_get_members', $user_addresses );
  	}
docs: Get user-mails from all users of a blog by a meta key and the exclusion value ( `!=` operator )
  
  @since  0.0.1
  @uses   get_users
  
  @param  string $current_user_email email of user
  @param  string $context should be 'comment' or 'post'
  
  @return array $users