I didn't read the email you sent me yesterday until today because I wanted to have something to look forward to.
I didn't open the email you sent me yesterday so that I would have something exciting today.
ーI didn't read the email you sent me yesterday until today because I wanted to have something to look forward to.
「何か楽しみが欲しくて、昨日送ってくれたメールを今日まで読まずに取ってある。」
didn't read the email you sent me で「私に送ってくれたメールを読まなかった」
look forward to で「〜を楽しみにして待つ」
ーI didn't open the email you sent me yesterday so that I would have something exciting today.
「今日何かワクワクすることがあったらいいと思って、昨日送ってくれたメールをまだ開けてないんだ。」
didn't open the email you sent me で「私に送ってくれたメールを開けなかった」
something exciting で「何かワクワクすること」
ご参考まで!