what? a "failsafe" system that sends you an email if your newsletter hasn't gone out by a certain time each day
why? in case you forget to send, or there's a technical issue that prevents send (for pre-scheduled newsletters), and you'd like the peace-of-mind of never worrying about that.
worth it? honestly, probably not given this current setup. Someone should make an easy way of doing this, and then it would probably be worth it, but unless you're regularly forgetting to send / facing technical problems with sending I doubt this is worth it for the amount of benefit it brings.
1) Make yourself a copy of the Newsletter Failsafe GoogleSheet
2) Give a complimentary full subscription to a special email address you have access to – if you're using a GMail-based service, I recommend email@example.com (you can add a + sign and then any word at all after yourname in a gmail address and it will still go to your main inbox; this is often useful for filtering messages).
Send a test-email from your newsletter to the failsafe email address.
3) Copy the Newsletter Failsafe Zap. (You may need to set up a Zapier account; the free tier will be more than enough for a daily newsletter or even 2-3 daily newsletters).
Fill out the Zap by selecting your email account and filtering all emails to your failsafe email address, then selecting the Failsafe Googlesheet – the other relevant information should be pre-filled.
4) Go to the Failsafe Googlesheet and fill out your newsletter name and the email addresses that should be notified if a newsletter fails to send. (You can send to as many addresses as you like, just separate them with commas). Don't edit any other fields, they will fill themselves.
5) Go to Tools --> Script Editor; this will open a new Script Editor Tab. Go there and click the "Current project's triggers" button (clock in speech bubble icon) in menubar; this will open a third new tab, the Trigger tab.
6) In the Triggers tab, click "Add Trigger". Choose function "ifNotSentToday". Select Event Source "Time Driven". Choose "Day Timer" or "Week Timer" according to needs, and select appropriate time. (You may want to test the system by setting a time before your usual newsletter send time, then once you see that that triggers the alert email as required you can go back and change the trigger to a time after your usual newsletter send time). Click Save and authorise -- all set!