简短一点的话：
Dear xxx（客户名字）,
We would like to inform that xxx（离职同事名字）has left our company with immediate effect.For any correspondance related to the products and services of our company,please kindly contact the undersigned.
We will continue to provide excellent services to you at all times.
xxx (你的名字,职位,公司名,联络号码）
2nd Sept 2009