1. thanks for your letter of/dated+日期
with reference to /refer to /in response to /in receipt of your letter of+日期
e.g. Thank you for your letter of 15,Aug,2016.
2. obtain/ come to know 获悉
e.g. We have obtained your name and address from the Internet.
3. take pleasure of / pleased to address(ing) this letter /email to you
with the hope of /seeking the opportunity of/seeking the possibility to
establish /enter into business relations with you
借此机会写此信/电子邮件建立业务关系。简述写信目的，还可以用最常规的，We are writing to…
e.g. We take the pleasure of addressing this letter to you with the hope of establishing business relations with you.
4. avail oneself of this opportunity / take the opportunity to introduce oneself to you
现借此机会向贵公司介绍，我们是XX。自我介绍，介绍公司类型，joint venture合资企业，foreign-owned/ state-owned enterprise 外/国企，private company 私企等。
e.g. We avail ourselves of this opportunity to introduce to you. We are a joint venture specializing in importing&exporting of garment.
5. enclosed please find our latest catalogue and price list/samples for your reference
e.g. As requested, we are enclosing our latest catalogue and some samples.
6. look forward to/await /wait for your early reply
e.g. We are looking forward to your early reply. Should you require any further details about our company and products, please do not hesitate to contact us.