You don't mention what $mailprog is, but assuming it's sendmail you might want to investigate the -odq option. If sendmail is running as a daemon on your system (look for something like /usr/lib/sendmail -bd -q15m in the process list), adding that option will not let the mail be delivered directly but instead queues it up for the next regularly scheduled time that sendmail will run the queue (e.g. -q15m means every 15 minutes). I'm not a sendmail guru, but it's my understanding that this will be more resource-friendly than starting up a synchronous sendmail process for each outgoing email.