They have the same meaning. And there is just the diference of the tone. For example, you can try to speak 收到了 and 收到, and their tone is different. 收到了's last word is 了, which is Tone 3. 收到's last word is 到, which is Tone 4, more powerful and shorter. And 收到 is more shorter than 收到了. So 收到 is more concise. In English, "have" usually doesn't change the tone of the sentence, because it's in the middle of the sentence. But in Chinese, 了 is usually the end of a phrase or a sentence, so it can change the tone.