1) Is it correct to use "should" in a sentence with the purpose clause in the Present. The matter is that I have been looking through some grammar material on the purpose clause and it drew my attention that all examples given in the Present, didn't have "should" in them. But the examples in the Past had "should" in them. For instance,
1) I am writing this letter so that he can/will know what has happened.
2) I wrote that letter so that he would/should/could know what had happened.
Would it be correct to use "should" in 1?
I am writing this letter so that he should know what has happened.