Caution! Some files may be harmful. Before receiving any files from any user, and even if the account from which the file transfer notice is sent looks familiar to you, it is strongly recommended that you verify that the person sending you these files is indeed the person you think he is, for example by asking him for some kind of information known only to the two of you.
Do you trust the sender? Are you sure the sender is who you think he is? Are you sure you want to receive the file?