Thank you! Unfortunately, I am unable to attach the context on this now. But I think I see what is an explanation for that.I think that you need to provide some context Gustav02. The meanings overlap, so the one to choose depends on the sentence in which it is to be used and the meaning you intend.
PS. Also note that I have edited your thread title so that it shows what your question is about.
Thank you for your comprehensive explanation! I see what you mean.The do not mean the same. A messenger brings a message. That message may be written, or oral, or take some other form. A messenger also does not have to be a man, but may be a woman, or a child, or anything at all capable of carrying a message:
The principal of the school asked Sally to act as a messenger, and sent her to all the classrooms in the school with a note for each teacher.
The Angel Gabriel was the messenger sent by God to the Virgin Mary to announce that she would be the mother of Jesus.
A delivery man delivers something. As the name indicates, a delivery man is an adult male.
The delivery man sent by the store where I bought my new dishwasher not only delivered it, but also installed it.
Because John was not at home, the delivery man left the package containing the Kohinoor diamond on his doorstep.