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 marketingcampaign 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…