To confirm the status of that message, go to your vcita Inbox, and select the thread you want to view.  This will take you to the Conversation with that client.  Beneath the conversation text box, you will be able to view the Read Status:

The Read Status will display the time stamp for when the message was sent, show if the message was delivered, and if your client read it. 

If your client reports not getting your message, please check this article for tips on making sure your emails are delivered and are not routed to spam.