some of our clients asked us to change the mass mailer plugin to limit the emails sent on the cron, as the actual one some times block the smtp or the hosting account if the list is a big one. so we have decided to look in the code and i have found a simple way to do the jobs, and since is simple we have decided to share it with the community . open the file plugins/mass_mailer/Cron/Email.php and change this lines (begin from line 55) while (($task = $this->MassMailerTask