reverse case to acknowledgement of one's letter

[kwfine]

When someone wrote a letter to me, on receiving the letter, I should write an acknowledgement to them. The letter's subject may be "acknowledgement of someone's letter".
Now the case is reverse, in which I want to formally ask someone whether they have received my previous letter
Is it correct if I write this as the letter's subject?
"Need your acknowledgement of my previous letter".

[Alan]

Yes.