Student or Learner
I am a bit confused. Do I use per his e-mail or as per his e-mail or further to his e-mail?
There are some professions where this type of language is used, but if your goal is simplicity and clarity (and that is the goal of my business writing) I suggest something entirely different.
As Mr. Smith requested in his email, I have scheduled...
As the client said in his email, his arrival time has been changed to ...
In his email, Jerry asked us to... I've taken care of those arrangements.
Or even switch the order around
I have scheduled a meeting for X and Y, as Mr. Smith requested in his email.
Please note that our clients are arriving now at 10 a.m. (does it matter that they sent an email about it?)
I've taken care of the arrangements Jerry asked for (in his email).
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.
Just 'per' is confusing, ornate, and archaic. It's Latin, and was used in expressions such as 'per yours of the 15th ult.' ('Yours' was a conventional abbreviation for 'your missive'; ult. was an abbreviation for ultimo, itself a conventional abbreviation for ultimo mensi - 'last month'.)
This sort of abbreviation did little to aid or advance communication, so people srted translating: 'as per your...'. This made 'as per' accepted in some circles, and people thought it would make them sound clever if they said thing like 'as per usual' instead of 'as usual'.
Avoid 'per' in this sort of context, unless you have the misfortune to belong to a business community that still insists on it.