Increase the "Email First 500 Candidates" tab to at least 1500 or more candidates

Currently, the limit of 500 for emailing candidates in a mass email has never increased. We consistently email more than 2000 (usually around 3500) candidates at given time when we have a new job ad. This is not spamming, but for candidates who already signed on to receive updates on jobs that fit their criteria. As it stands right now, it can take up to 30 minutes to run a single job ad. Increasing the number to 1500+ would ad so much more efficiency to what is being performed daily for us.