In References to - Re
This letter has beeb drafted in an effort to help you evaluate my proficiency in English language as per the present selection requirements.- the use of the passive suggests that you didn't write the letter ytourself. Use the active.
Bussiness- spelling, and I don't see the need for the capitalisation here
graduation and Post Graduation- university and post-graduate
After post graduation- Since completing my Master's degree (or whatever it was)
in the english- no article and capitalise
which became my major speciality- punctuation and why not 'I have specialised in'
USA - article
till date- till now
communications is- agreement
good grasp in- a...of