Please reply to all.
请全部回复。
When you reply to this e-mail, please hit "reply all" so everyone will know what's going on.
当您回复此邮件时，请点击"全部回复"，这样所有的人都能了解情况。
Please "reply to all" when you respond to keep everyone in the loop.

回信请点击"全部回复"，以使每个人都了解情况。

I cc'd you.
我抄送给您。
I cc'd you, so you'll get the e-mail as well.
我抄送给您，这样您也能收到此邮件了。
If you don't want to disclose the recipients, you can put them in the "bcc" area.
如果您不想公开您的联系人,您可以将其放入"密送''区。