Quite often it is said that the key to staying healthy and happy at work is to have a good work life balance. This usually means that you should be keeping your working life and your home life separate and have the ability to turn work off when you leave the office for the day.
Increasingly, millennials and younger generations in the workforce are looking for a work/life blend. They are willing to put in those extra hours and answer emails after work from home but the opposite also needs to be true to maintain balance. As an employer, if you expect to intrude on your workforce during their leisure time then you should expect that their leisure time can also intrude on their time in the office.
Millennials are extremely social, starting families, and are starting to have increasing responsibilities outside of work and want the flexibility to take care of things as they come up. The key is balance. Strictly enforcing rules to restrict private life interactions in the workplace will most likely lead to resentful workers that simply hide their behavior.