Unfortunately, in my experience, it doesn't work. At least in challenging schools or those with weak leaders. I recall at least three big culprits who used the system and sent 9 to 10 emails each weekend on a regular basis. Sadly it meant people 'felt obliged' to respond to emails then and there due to worry and the stress of leaving it till Monday. It also allowed the culprits to get lazier. They always sent late and last minute emails but they wrongly pouted they were sending them 'early". A clear, transparent, fair and equal policy for all is better than a 'there are emails there for you in case you want to work all hours' one.