The information you requested is being forwarded to you under separate cover.

现另函寄上所要资料。

《牛津词典》

I am sending the copy under separate cover.

我们将另寄一份同样的合同。

youdao

We will send you under separate cover catalogue and pricelist.

关于目录与价目表，我们将另邮寄给你方。

youdao

Under separate cover, Arianda sent her own letter, with a drawing of the American and the Ukrainian flags.

NEWYORKER: The Natural