I'm wondering if there is a way to have multiple REPLY to addresses in Outlook Express.

My boss wants me to email him all the emails I send out to clients so I put both the client and his email in the To field.  However, when the client replies is there anyway that the reply email will automatically go to both my email and my boss' email addresses?

You can't rely on the client to hit "reply all" instead of just reply even if I ask them to in my email so it goes to both of us.  I am only part-time so if I'm not here when the client responds, he will have to wait until I am in the OFFICE to forwad to to him.  It'd just be easier if 2 email addresses could be put in the reply to field in the ACCOUNT options.

Thanks for your help.I found that Outlook Express cannot do this but MOZILLA Thunderbird will.  So I've switched email programs and mission accomplished.That's interesting.  Thanks for letting us know.  SOYBEAN,
Isn't this possible if the addresses are in the same line (reply to ) in Outlook ? ?
I know hardly anything about Outlook or Outlook Express but i seem to remember reading this somewhere.patio,

I just tried it in Outlook and it did not work.  I tried separating multiple addresses with a comma or semi-colon in the Reply to box in the account settings and Outlook would not accept it. 

Another way the OP's requirement could be handled is by use of a mail forwarding feature, where the feature is enabled via settings in their email service.  Even a free Gmail account has this feature.  So, when sarah is away, she could logon to a Gmail account, enable forwarding, which automatically forward mail sent to her address, to her boss's address until the setting and disabled. Or, they could leave it permanently enabled and set Gmail to keep a copy on the server so that she could download those messages she missed while she was away.

Web hosting services also typically offer mail forwarding.  So, if they have a business website, this could be another way to enable mail forwarding.I know Outlook and Outlook Express handle "Rules" which could potentially forward every single email, but, on a server level as Soybean mentioned would be much better.

Even better:
Why not just have the boss add your work email address to his own client if he is going to check every email anyways? It would be less time for you and him to be wasted.