1. I am writing to confirm /enquire/inform you…
我写信时要确认/询问/通知你…

2. I am writing to follow up on our earlier decision on the marketing campaign in Q2.
我写信来追踪我们之前对于第二季度营销活动的决定。

3. With reference to our telephone conversation today…
关于我们今天在电话中的谈话...

4. In my previous e-mail on October 5…
先前在10月5日所写的信…

5. As I mentioned earlier about…
如我先前所提及关于…

6. As indicated in my previous e-mail…
如我在先前的信中所提出…

7. As we discussed on the phone…
如我们上次在电话中的讨论…

8. From our decision at the previous meeting…
如我们在上次会议中的决定…

9. As you requested/per your requirement…
按照你的要求…

10.In reply to your e-mail dated April 1，we decided…
回答你在4月1日写的信，我们决定…