Dear …
I want to thank you for extending the offer to me for permanent employment with __(name of organization)__. I am absolutely delighted to have been offered this opportunity. Please also allow me to extend my gratitude to you for all your support and encouragement during my probationary period.
I have found __(Name of organization)__ to be a wonderful atmosphere to work in during my tenure here thus far. Already I have developed a fondness for all the people here. You have a way of creating an environment that allows your employees to flourish and grow and I am so grateful and proud to now be a permanent member of your team. All of it was greatly appreciated.
Once again, thank you, __(Name)__. I look forward to a long and rewarding career with __(Name of organization)__.
Sincerely,