By adding an email address for Reply-To, Luminate will insert that email address in the "Reply-To" email header. Not all email clients are configured to use the address in the Reply-To header when the users reply to messages. Some email clients will always use the From address instead of selecting the Reply-To address. This behavior is controlled in the email clients, such as Outlook, Thunderbird, etc. Luminate Online doesn't not have any control over which email is ultimately used in replies; all we can do is insert the email address in to the Reply-To header.