It's exactly the way native Vietnamese speakers say "I've just received a letter". There is no translation equivalent for "được" in this case, so it can't be translated into English.

I just want to add a few points that you might find useful. "được", "mất", and "ra" belong to a kind of adverb (which follows a verb) that expresses the result of the action. For example: Tôi tìm được/ra chìa khóa rồi. (I found the key - while if you say "Tôi tìm chìa khóa rồi", it only means "I looked for the key). Anh ấy đi mất rồi. (He's already left - if you say "Anh ấy đi rồi", the hearer can understand that he is not here anymore, but for someone that doesn't know the situation, the sentence "Anh ấy đi rồi" can also mean "He's on his way" as "đi" alone only means "go"). Another example: "Tôi nghĩ ra rồi" - I've figured it out! while "Tôi nghĩ rồi" (without "ra") means "I thought about it". I guess English doesn't have this kind of adverb, and the difference in meaning is often expressed by using a total different verb rather than adding an adverb like this.

You can write: Tôi vừa nhận 'được' một lá thư. But you dont write: Tôi vừa đi 'được' đến trường. In case, it's : Tôi vừa đến trường. :))

thank you Bianca ^_^

"được" is used here to imply that you got/gained something. For example: Tôi tìm được chìa khóa rồi. - I found the key already; Peter vừa học được một từ mới. - Peter has learned a new word.