BEC Writing

I noticed to you that you will attend the English Training on 20th November, at 14:00-15:00. We have a new large export order, which speaks English only. Thus, according to the necessary, we need to all of sales staff to attend this training. Please attend on time. Thank you for your cooperation.

"order, which speak", an "order" would not normally speak.  An "order" is paperwork.  A customer normally speaks.

We have a new large export customer who only speaks English.

Thus, through necessity, we need all sales staff to attend this training.

"according to the necessary," I would not use because it is really not necessary, and weakens the sentence.