Recently encountered a frustration where contact emails coming through our Joomla 2.5 website we showing our own email address as the reply-to address instead of the client’s email address so we had to copy and paste their address into a forwarded email to reply to the client. Just clicking reply would reply to the email to ourselves.
Found out that it is not a Joomla problem but rather a logic misfire on Gmail’s part, where it was seeing that we were sending the email to and from ourselves. We just changed the Joomla configuration for the sent-from field and it cured the misfire.
We found the solution here. Let us know if this helps you.