This is the 471st most frequent Chinese word.
来自
"To come from" or "originate from."
Here, "来自" is used to indicate the speaker's origin or where they are from, commonly used in stating one's nationality or birthplace.
我来自中国。
I come from China.
In this sentence, "来自" indicates the origin or source of the letter, showing who sent it.
这封信来自你的朋友。
This letter is from your friend.
"来自于" is used here as a way to explain the source of an abstract concept such as inspiration.