word order - 日本へ手紙を送る vs 手紙を日本へ送る

I'm trying to learn the ropes of Japanese language with some online guides, and sometimes I try to anticipate the sentences using what I learn, just to find out that the guide uses a different form. Now I'm aware that a thing can be said in different ways, but let's go to the problem.

The guide was explaining the sentence "Send letter to Japan", now using what I learned so far I started composing the sentence from the destination, which is Japan (日本) and being it a location target I used the へ particle to connect it with the letter object (手紙). Now I have a letter to Japan, which is the object of my sentence, so I connect it with the を particle and finally the action to send it (送る).

Google Translate agrees with me that 日本へ手紙を送る is "Send a letter to Japan", but the guide uses 手紙を日本へ送る, which is clearly also correct.

Now to the question: are both these way of saying "Send a letter to Japan" correct or is there a preferable one?

Answer

1) 「日本{にほん}へ手紙{てがみ}を送{おく}る」

2) 「手紙を日本へ送る」

Both are correct and grammatical. As far as pure grammar, neither is any "better" than the other.

Japanese grammar is indeed more flexible than it seems to be taught outside of Japan (particularly at the beginning level). As long as the correct particles are attached to the right words, the word order can be switched around fairly randomly if it is for the grammaticality (if not for the subtle nuance and/or emphasis).

While both phrases are "correct", there would be a difference in the actual frequency in which native speakers would utter/write the two phrases. You would see/hear #1 more often than #2.

That is because in phrase #1, the direct object 「手紙（を）」 is followed directly by the verb 「送る」 with nothing in between. #2 has 「日本へ」 in between. This makes #1 sound slightly more intuitive or "neutral" if you will.

For this reason, 2) 「手紙を日本へ送る」 could sound as if the speaker/writer were placing an amount of emphasis on the 「手紙を」 purposely. An example of that purpose would be to imply that it is a letter and not something else that s/he is wanting to send.

Thus, unless one has a reason to use #2, #1 would be the more useful structure. Once again, as far as grammar, both are "equally" correct.