The mail address that you "reply to" depends on what the original sender has set up for their e-mail address in the client. For example, I could send you an e-mail but I could set my client up to say that it came from chris@doohicky.net. When you reply to that e-mail you will be sending to chris@doonicky.net. As this is not actually my e-mail address then I will never get the reply.
So, if someone who had sent you the e-mail hasn't put their e-mail address in correctly on the client then they won't get a reply.
Chris.
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Chris Andrew, CCNA, CCSA
chris@iproute.co.uk
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