I will not run it every 15 seconds.
here's what we're doing so you see why we can not use announcement lists or some other built in dreamhost alternative.
A catch all is set up for our domain. The script checks for new incoming email and based on the original address it was sent to, forwards to either the appropriate person or appropriate group of people. The appropriate people change regularly and are read in from a database of emails and preferences.
When the script runs, if there are no new emails the full extent of processing done is:
include 3 files
read other files from a directory
if there are no files in that directory, exit
So it is efficient, but I will run it every few minutes, also as sdayman pointed out, which I had not thought of, it can run at different intervals for different times. In the night it really can run periodically while in the day it can run more often.
Thanks, I really am open to any ideas or concerns.