How to identify a spammer?

Question

Fight against spam

I need to write a program that determines who the spammer is. I have a file with the senders' mails and their messages. The content of the message is not there, but there is simply data that they sent to me. What parameters should I pay attention to?
Please write at least a small algorithm or pseudo-code of the program, so that it would be clearer what I am writing.