If I don't understand the client, I would inquire my officemate first, If I still don't get it I will come back to the client and make everything clear in order to avoid thig kind of things happening again. I would reply the client after I totally understand the meaning of the email in the future. I have took a lesson from it.
看样子你像外贸人, 我以前也是, 理解你的处境, 如果这是封给上司的道歉信,我想写成这样也就ok了,做外贸要小心处理email,否则损失真的不是你可以承担的.^-^