You can create an autoresponder for your email by logging into Webmail.
In Webmail, click on your email address in the blue bar and select Auto-responder below it.
Autoresponder
In the page that opens, click the blue Add an autoresponder button.
In the page that opens, enter 8 (hours) in the Interval field.
In the Subject field, enter the title of your answer
In the body text field, enter your actual voicemail message
Define Start and Stop at the time the answering machine is active
When you're done, click the blue Create / Edit button at the bottom
