Hi [name],
By the end of this exceptional year, may I express my gratitude for all the hard work of you and your team? I would also like to take this chance to conduct a short review of what we have done together during this uneasy year. It is going to take a while but I am sure it worth.（很普通但必要的开场白，毕竟不论今年的结果好坏，感谢人家的努力总是没有错的。这已经跟在大街上只要见到人都叫靓仔靓女是同一个道理）
Worldwide, we have Covid 19 and trade conflicts this year; internally we have problems related to raw material, exchange rate, and so on.（大环境就这么一句好了，不用写多） Despite all these difficulties, we managed to maintain our business relationship fairly success. In the figure below you see we were not so smooth earlier but the latter half of the year orders grow stronger and result in the same level of demand as last year. （上文说的第二点，数据。不要大篇幅把数字写出来，没意思的。能用一张图表解决的事，就不要用文字）The XXX project/product worth highlight as a single product with the strongest growth (you purchase more than 10 containers which contribute to 25% of our total volume). （像这样的highlight少量数字倒无所谓。在这我把某个做得特别好，或是种种原因特别值得一提的项目拿出来说） Although it wasn’t an easy start, we learn from the mistake and move on. The quality problem was recovered and stamped to the heart of our workers so much that their sense of quality is highly improved. The problem fixing experience turned out to be our strong competitive which facilitate us to become your supplier of priority. （以上文说的套路，我把其中一个重大客诉事件拿来做营销。Supplier of priority 一定比什么鬼 important long term partner高多了。）
Moving forward, we want to do more business with you. (Of course!) （当然是想跟你做多点生意啊，不然我图个啥？但怎样用一个展望的方式拉入来呢？）This is already our 3rd years of relationship and we do enjoy working together with a business like yours. We are developing more products for your choice. We are building up a stronger team to serve our customers better. We are trying to extend our capability to make goods available to you more locally in a timely manner. （来了。今年我们在人力，在物流，在产品都加大了投入，这是我们展望的好将来。而这些东西最终都会benefit我们亲爱的客户身上，所以，你还不下单？）Many good things going on, and I hope you can be our witness. （用川宝的英语，a lot of good things happened，而我们诚邀你做我们成长的见证，相当得体的话）
Best,
Your Name (Sales Manager)name@yourcompany.com+(86) 131-1234-5678Street, City, Province, China yourcompany.com