This guide shows how you can enable auto-reply for your email accounts.
Log in to Plesk control panel using your administrator credentials or the specific email user credentials. Choose 'Mail' from the left menu, and click on the desired email account name.
In the next view select the 'Auto-Reply' tab and you'll see the settings for the reply. Select 'Switch on auto-reply' and insert your message in to the text box. You can optionally choose a date when the auto-reply will automatically be turned off. Finally save the settings by clicking 'OK'.
When you want to disable the auto-reply, return to this menu and untick the box 'Swith on auto-reply'. Save the change by clicking 'OK' at the bottom of the page.