Notice letter still valid

In a business letter I'd like to explain to our client that the notice letter I posted 3 moth ago is still "valid".
Can I phrase it like this:
"My notice letter posted on 03/10/2012 is still in force." - it sounds to me too legal as our company is not an authority.
or
"My notice letter posted on 03/10/2012 is still in place / valid." - I dont know wheter it means I wanted to

Any other suggestion?