一般在外贸英语中，或者在给国外人的邮件中经常要用到请知悉和已知悉这个句子，下面列出了各种英语的表达方式

请知悉
后面跟一个句子，说明要知晓的事情：
Please be informed that...    
Please note/please learn about that...
please know/learn/ acquaint that...
Please be advised that.....
Please be informed that.....
Please be notified that....

前面说了一些情况，最后说这句请知晓：
Please be noted / Please note. 
Please be informed.
pls be kindly noticed.

eg. Please note it is important you continue to report errors so analysts willhave data to analyze and correct the problem ASAP.
Please be informed that your application for the fee has been approved by our operational manager. 以上请知悉，谢谢！

以上请知悉
The above please learn about, thanks!
I have to inform you about that.
Thank you. Please be aware of the above.
Above, please know.

已知悉

Thank you for your information/email.
The information is well received.
Knowledge receipt of your email.
It has been informed.
It has been noticed.

简单点，也可以这样说：
Noted.
Well noted.       well程度好一点
Well noted with many thanks.     已知悉，非常感谢。
Thank you for your notice, I have received. Good luck!   
谢谢您的通知，我已经收到了，祝好。