I thought this was a standard function which a email suite like Smartermail should already be included. But I was wrong!
Migrated a client from godaddy to smartermail. One feature that the client asked me is how to schedule an email for later delivery... It's pretty embarrassing for a full fledged email suite to miss a important business function like schedule an email. Especially if it's the enterprise edition
If godaddy webmail have this function, Smartermail should have it...
See this link ca.godaddy.com/help/scheduling-a-time-to-send-email-messages-2768