How to say “I look forward to your reply” in Japanese?

I wanted to say “I look forward to your reply” in my email to a Japanese colleague. So I checked it up on Google and wrote “あなたの返事（へんじ）を楽（たの）しみにしています。Anata no henji o tanoshimi ni shiteimasu”. However, he laughed at me and said my email looked like a love letter. How should I say it?

Answer by Japanese teacher

(1) お返事（へんじ）／ご返事（へんじ）をお待（ま）ちしています。
Ohenji / Gohenji o omachishiteimasu.
I look forward to your reply.
(2) ご返信（へんしん）をお待（ま）ちしております。
Gohenshin o omachishite orimasu.
I look forward to your reply.

Explanation

Online dictionary is useful for a quick translation to grasp the meaning but the translation rendered may not be culturally or socially acceptable.
“Tanoshimi ni shiteimasu” (looking forward to something) is appropriate if you are talking to a friend or writing a personal letter but not so for business.
For business, you can use the suggested expressions instead.

In the first expression, both “ohenji” or “gohenji” (your reply) are acceptable. Traditionally, people use “gohenji” but recently, more people are using “ohenji” instead.
The second expression uses “omachishite orimasu” (waiting) which is a more polite (or humble) version of “omachishite imasu”.
If you are more junior than your colleague, you can consider the second expression instead because it is good to humble yourself in front of a more senior colleague.