I would like to inform that today is my last day in XXX company. It was really great working with you all and had a great experience and learnt many things in all these 5 years.
I would like to thank you all for your great support and cooperation during my tenure.
You can contact me in my personal email id: firstname.lastname@example.org
I would like to take this opportunity to introduce Mr.John who has joined in XXX company replacing me,I would request you all to support him in her long way to enrich her career, you can contact him in email@example.com (9876543210).
Thanks and Regards,
Another sample: http://www.lettersamplesfree.com/2016/02/last-working-day-letter.html