I TRY not to email while they are on vacation. However, both of my Ts have said it is okay but we also discuss that it may take some time for them to check their messages and repsond. T is in vacation this week and she told me to text her of I need it. She will likely not heck her work messages often but she knows often just writing it down and sending it to her is helpful. If she did not say it was okay to message her, I would not.