The Greek word translated when you received
is παραλαμβάνω (paralambanō). It is a technical term for the reception of oral tradition—a set body of teaching which is passed on in a controlled and accurate manner. We find the same word in 1 Corinthians 15:3, where Paul states: For what I received [παραλαμβάνω/paralambanō] I passed on to you as of first importance: that Christ died for our sins according to the Scriptures
(NIV). In this passage Paul is saying to the Corinthians that he passed on to them a body of teaching about the death and resurrection of Jesus which he himself had received from others. (That body of teaching—or at least a summary of it—is detailed in 1 Corinthians 15:3–7.) Paul passed a similar body of teaching on to the Thessalonians, and they in turn received
that teaching from him. This particular act of receiving involved facts and information more than the inward acceptance of the gospel.1
13 And we also thank God constantly for this, that when you received the word of God, which you heard from us, you accepted it not as the word of men but as what it really is, the word of God, which is at work in you believers.