I would like to give you a heads up that I will be officially on maternity leave, commencing from ......(date)........"
"The actual commencing date is yet to confirm. Once fixed, a notification will be sent to you."
"Please/kindly be advised/informed that all your inquiries will be taken care by Mr.......(name)....... Thus, from now on, I will include him in the communication. Please feel free to loop in Mr.......(name).....and leave him in CC line"
"My expected return date is ...............(date)............"
"During my absence, Mr.......(name).......(email) will cover me on...........(duty)..........."
"Should there be any doubts or concerns regarding payment matters, please contact Mr..........(name).......... email....................."