How to write 'I'm emailing you in regard of [topic]'

Question

I'd like to ask whether my writing is correct or not; I'm trying to write a formal email following up my previous email in regard of topic X. The way I write it is like this :

Xデモ​依頼​について,メールをお送りします.

I was wondering if this is the correct way to say it - it make sense in English but seems awkward in Japanese.

In general this is what I'm trying to write :

Xデモ​依頼​について,メールをお送りします. ​突然のメール失礼いたします。

​先日​​送らせていただいたメールですが,ご確認いただけましたでしょうか​​。​

Xに関連するご質問がございましたらお気軽に​​​​お問い合わせください​。

お返事をお待ちしております.

Any suggestions to improve my awkward email is very much appreciated, thankyou!

Answer 1

You can omit "突然のメール失礼いたします。". This sentence is normally used when you have never sent the email before.

With regard to the first sentence, Xデモ​依頼の件​についてメールをお送りしています。 would sound more natural.

All the other parts are perfect.

Answer 2

You can use:

Watashi ha [topic] ni tsuite meeru wo kaiteimasu. (私は[topic]についてメールを書いています)