1) Make sure NetworkManager is installed

2) add

export PYTHONPATH="${PYTHONPATH}:/home/user/Documents/rasp" #"rasp" is the module containing python-function for sending the mail
export EMAIL_USR="[email protected]"
export EMAIL_PWD="strong_password" 

to ~/.profile

3) go to /etc/NetworkManager/dispatcher.d and add the send_mail file here.