This Exchange question here: Staying in contact with clients when I have a different sleep-wake rhythm (being a night owl or living in a different time zone) deals with the subject quite well, but it is more focused towards a specific problem. This question is quite generic. That being said, if this is mainly down to opinion or too broad I do apologise.
Normal business hours are Monday through to Friday. Usually 9am until 6pm (or very similar). Is it considered then bad practice to email clients during the weekend; large organisations within the creative, digital industry do not work weekends. The weekend is a time of rest.
Should all business communication be kept to normal business hours? Would you say you significantly increase the risk of your client taking a dislike to you if you email them at the weekend?