RTNADDR is another optional parameter which specifies the default from address. Most email clients have a similarly named field in their setup parameters which saves you from having to type the "From" address on every message. (In the case of EMAILX, you aren’t likely to be "typing" any addresses, so the point may be moot.) Note that you can always supply this information directly in the message header (either in header or body) by including a line consisting of "From:" followed by your email address. Note that you can use the extended addressing syntax here (optionally including a text name followed by the real email address in angle brackets, e.g. "Administration <admin@microsabio.com>". You can of course skip this parameter and include it directly within the header and/or body parameters.