1. You will receive a discount by ordering today.
今天下订单的话有折扣。
还能这样说：
We will discount the product if you make an order today.
We'll give you a discount if you make a large order today.
应用解析：
on order 定购中（发货而尚未交货）；
on the order of 属于……一类的，与……相似的

2. We are glad to receive your order and confirm our acceptance for it.
我们很高兴接到你的订单并且确认可以接受。
还能这样说：
We are pleased to have your order and it is certain to be accepted.
We make it certain that we can accept the order which we are pleased with.
谚语：
Glad children make glad parents.
孩子好，父母笑。

3. Your order can go out next Monday.
你的订单下周一就可以出货。
还能这样说：
Your order can be sent next Monday.
Next Monday, you can have the receipt of the order.
谚语：
Out of the (frying) pan and into the fire.
跳出锅里，掉进火里。

4. The trouble is that the factory is running at full capacity.
问题是公司的订单已经满了。
还能这样说：
The problem is that the order is full.
What matters is that the factory is fully engaged.
应用解析：
full of admiration 怀着钦佩的心情；
full of the roof （旅馆等）住满了人的；
full to 满到……；
full life 有丰富经历的一生