Security firm Proofpoint discloses a mechanism by which Google Apps Scripts can be used to deliver malware.

Google Apps Script abused to launch dangerous phishing attacks Criminals hijacking subdomains of popular websites such as Bose or Panasonic to infect victims with malware: here's how to stay safe ...

The script then adds a label to those emails so you can easily find them and decide if you want to send another reminder email.

Sort of. If you know JavaScript, you can use Google Apps Script to add features to many Google products including Gmail.

How to add scripts to Google apps If you’re comfortable with JavaScript, you can write your own original programs. Just open Docs or Sheets and go to Extensions, then click on Apps Script.