To enable the auto-responder on an email account, follow these steps:
Log into to your webmail interface (http://webmail.yourdomain.com) with the full email address of the user for whom you want to add an auto-responder message.(email@example.com)
Once in the SmarterMail interface, click the "Settings" link on the left-hand side navigation menu (it is an icon that looks like gears).
Click to expand the "My Settings" folder.
Select the "Options" tab if it is not already selected.
Check the box next to "Enable auto-responder".
Check or uncheck the other boxes according to how you want the auto-responder to behave. "Disable responses to indirect mail" will prevent the auto-responder from responding to email not directly addressed to you (for example, an email you get because you are listed in the CC: field). "Limit responses to once daily" will prevent the same sender from being sent an auto-response more than once a day.
Click the "Auto-Responder Message" tab.
In the "Subject" field, enter the subject you want the automated response email to have.
Select "HTML" or "Text" from the "Compose Format" dropdown box. Note that some email providers may be more likely to mark HTML email as spam, so you may want to select "Text" to make sure the recipient sees your response.
Enter the body of the automated response in the "Message" text field.