Acknowledge receipt explanation

[guestpak]

Could you please telle which one of the following is correct one?

1. We acknowledge receipt with thanks your letter dated.....

2. We acknowledge receipt of your letter dated.... and thank you for your interest in our Magazine.

3. We acknowledge receipt with thanks of your letter dated.....

Please clarifiy if 'of' is optional here.

Thanks

[Conchita]

The second and third sentences are standard English. 'Of' is not optional, since you acknowledge receipt of something.