"I do not even know your name, yet you have my sincere thanks."
I offer my sincere thanks to you and your office.
As always, you have our sincere thanks for taking the survey.
To it I would like to add my own sincere thanks.
So let me express my sincere thanks to them too.
Again, sincere thanks for all the work you have done.
I would like to express my sincere thanks to everyone involved.
I would like to express my sincere thanks to them.
For this, I offer my very sincere thanks to everyone.
For this I would like to offer you my sincere thanks.