To configure reply to email address you will need to create an ALIAS first:

1. Click on the User for which you want to create an alias.
2. A new “User Info” window opens up.
3. Scroll down and locate “Exchange Info”.
4. In the E-mail Prefix add a new row. For example if the e-mail address will be “news@your_domain_hosted_with_us.com” then enter news.
5. Click below the option “Domain”.
6. You will be provided with the list of domains hosted with us.
7. Select the Relevant domain.
8. Scroll down and click on Update.

Once you have created the ALIAS- open the Use Info page and scroll down to Exchange Info section.
Then right click on the email address you wish to set as reply to email address and hit Promote and update.

Related Links :

MOSS Hosting

Business Email Hosting

Hosted Apps – Exchange SharePoint

Microsoft Office SharePoint Server 2007

Hosted SharePoint Exchange Services

Free SharePoint Hosting Application Templates

Hosted Exchange Provider