If Saffire is hosting your email, you can set up an out-of-office auto-response for any of your email accounts:
1) Go To http://webmail.yourdomain.com
2) Login to your account (full email address for username)
3) Once logged in click on Options
4) Expand "Mail" on the left
5) Click on Auto Response
From this page you can turn on and edit the auto-response from this mailbox.