YOU SAID:

I am sorry for not replying to your email.

INTO JAPANESE

あなたのメールに返信しないのが残念です。

BACK INTO ENGLISH

It is a pity not to reply to your email.

INTO JAPANESE

あなたのEメールに返信しないのは残念です。

BACK INTO ENGLISH

It is a pity not to reply to your email.