how to reply to a thread

Daniel Trierweiler <[email protected]> Sat, 16 May 2015 15:03:44 +0200
Newsgroups gmane.network.simulator.isi
Message-ID <[email protected]>
Hello,

the question may not really belong to ns and may even sound a little 
odd, but how do I correctly reply to a question in the mailing list?

Do i have to recite the Message-ID? And if so, where?