USPS informed delivery is pretty accurate and is a good way to know what mail you're getting soon.
The USPS sorting machines take automatic pictures of the letters that come through their machines that are on the way to you.
Then the images are automatically uploaded to the USPS servers for informed delivery.
I use USPS informed delivery myself and have noticed that it has been near 98 percent accurate when it comes to mail coming to me.
Although sometimes it may say that a certain piece of mail is coming on a certain day but then it does not actually arrive at the local post office to be delivered that day.
I've heard of some people accosting some mail carriers because a certain piece of mail was not delivered that day but it's not their fault.
USPS informed delivery does not guarantee a certain piece of mail will arrive on a certain day but it's pretty accurate.
Just don't be disappointed or mad if some mail does not show up on time.