How can I setup manual email filters

I have an email set up that sends alerts to various emails and I know you’re thinking that there’s probably a better way of doing this, I know, I just haven’t figured it out. Anyways, here’s my setup:

I have some server side scripts that run some checks and if certain things are met, it sends an email from alerts@localdomain .com to emaillist@localdomain .com. All of those emails are then forwarded to a few other emails that need to receive the alerts (Remote emails). My issue, well might be an issue, is that if some online bot stumbles across the emaillist@localdomain .com, then there’s a possibility that all the emails in the list get spammed by junk that shouldn’t be there.

I guess I have 2 questions here,

 1. Is there a way to set up manual email filters so that an email can, in this case, only receive emails from a certain address but send to multiple others?
 2. What would be the better approach to this in the first place? Is there a way to have the script send to an email list instead of an email? And, yes I know that I can easily set up the script to send to all the emails in the list, but the way its set up is that it can only send emails to one specified email.

I am fairly new to all of this and any guidance would be nice, thanks.