A colleague has this prominently in her #emailsignature:
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Our working hours may differ.
Please don’t feel obligated to reply outside your normal working hours.
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I work with people across time zones and am a night owl, on a 'maxiflex' schedule - and so TOTALLY respect and support this!
#WFH #workfromhome #emails #latenight #workinglate #reply #replytoemails #NotLandingAeroplanes