Question:
Is it allowed to bring a letter (addressed to a Non-Jew) on Friday to a post office (the post’s emoloyees are not Jewish), so it would be probably transported/delivered on Shabbat?
Answer:
It is permitted because the gentile is not doing the work for you specifically, rather because he was hired by the government to do a job. Besides he wasn’t told specifically to deliver it on Shabbos.
Sources:
O”C 267-5 M”B ibid 18.