Question

I had all ready posted the letter

Answer 1

If we have to change the speech then the answer is :---

The letter had already been posted by me.

Answer 2

$\huge{\bold{\red{Heya!!!}}}$

$\bold{\blue{Here\:is\:your\: answer\: }}$

I don't understand your question.

But I can help you a bit

If you want to change it Into passive Voice

so your Answer is here-

The Letter had already been posted by me.

$\bold{\green{✓✓✓✓✓✓✓✓✓}}$

$\bold{\red{Hope\:it\:will\:help\:you\:}}$