In any event, this rule is real for a couple of reasons. On the other hand, time zone considerations have to be made. Given, web is always on. Also, morning somewhere else. So, we can reasonably communicate.
Now, similar to artificial intelligence identifying irregular late emails are questionable. At least, from a conservative standpoint. On top of that, we can schedule sending. As a result, no excuse.
No Late Night Emails Send During Normal Hours
Then, the lesson is to send email during normal hours. To be on time is normal. A little early is better. Then, less than normal is worse. It follows, we make our own hours in some cases. Thus, within our range of acceptable activity.
So, we question actions outside of the norm naturally. After, we tend to question anything that is not clear. As a result, late night messages are questionable.
Therefore, could be a good answer. Programmers are notorious for coming up with a break through during late night coding sessions. Reason why we sent that message was that we just finished.