常见的商业信函开头有三种：

1. We are writing to enquire about...

该句型用于咨询。如：

We are writing to inquire about the trip to America your travel angency organizes.

我方想咨询一下你们旅行社组织去美国旅行的事。

2. We are writing in connection with...

该句型用于进一步了解对方广告上的信息。如：

We are writing in connection with the ads in the newspaper last Friday.

我方在上周五的报纸上看到一则广告，想进一步了解相关信息。

3. We are interested in ... and we would like to know ...

该句型 用于询价。如：

We are interested in your new mould and we would like to know the price of it.

我方对贵方的新模具感兴趣，想询问一下价格。

欢迎补充。