Do the scripts entered in the Server Scripts screen reflect new records only? Or do they cover exist

Summary

Entering a script in the Server Scripts screen functionality issue

Content

Hello all,

I am currently in the Application Composer > Contacts > Server Scripts and thanks to an answer provided in my past question I have the below script for making the Email field mandatory in the Contacts screen:

def email = nvl(Email,null)

if(email.first() == null)

{

return false

}

return true

Using existing contacts that were defined prior to the script, I removed the email value in the Email field and when saving the record the system saved successfully. So my question is, does the script entered in the Server Scripts entered only cover the newly created records? Or is there a way to include existing records that were defined before entering the script.