It is proper Netiquette to refrain from sending messages late at night. Don't send late night emails.
The hours of 10:00 PM to 6:00 AM are generally considered sleeping hours. Sending personal or professional email messages during this time frame may call your life style into question.
It is proper netiquette to refrain from sending email late at night because it may call your life style into question.
Send messages during normal hours or it may call your lifestyle into question.