Here’s the scenario: you have a second gmail account that gets email infrequently, but you need to monitor it. For whatever reason (company policy, in my case), you can’t forward the email to your main account.
I discovered that I could log into the second Google account and attach a Google Apps Script to a spreadsheet. The script monitors the gmail account for unread threads. If it finds any, it sends a message to my main account. The script has a time-driven trigger that can be set to run as frequently or infrequently as desired.
To use the script, make a copy of this spreadsheet. Open the spreadsheet and edit the cells that contain the email message parameters. Then go to Tools – Script editor. Choose Resources – Current project’s triggers. Add a time-driven trigger that runs the script as often as you’d like.